It appears that most people who are serious about drums use the popular drum programs like EZ Drummer, Superior Drummer, Addictive Drums, Session Drums, etc. I have several of these two and have worked with them but I never was convinced that they sounded any better or were any better in other ways than good drum loops, such as Drums on Demand.
     Personally, I'm not a drummer and I'm not a programmer, and I've never really liked working with midi. I can't imagine ever working with the piano roll or drum maps, or anything above entry level use.  I'm not going to go in and adjust settings for each individual drum and mix them, and go to any kind of elaborate or even semi-elaborate procedure. All of that is its own specialty and art.
     We've always gotten a great tone with Drums on Demand, and other loops too, especially now that there are so many presets on reverb and EQ to really make them pop. I can't imagine any basic beat or drum part that a drum program can do that I can't find something exactly or very close to it on Drums on Demand. Some people have all the ability and patience to sit there and program drugs and work with maps and midi stuff, but that's just not me. However, I don't mind working with loops and even slicing and dicing them for different beats or patterns, fill, turnarounds, etc. that I need. 
     The friend I collaborate with the most also uses Sonar and various loops including Drums on Demand, and we're trying to keep as much as we can on our DAWs the same so we can swap projects back and forth if I want to add a guitar or he adds bass, or if either of us wants to tinker a little with the drum EQ or reverb. I don't see either of us ever getting seriously into drum programming or working with drum maps or a lot of midi.
     Finally, we're not trying to cut an album. We do home demos. We do this for fun, and we also pitch some of the songs in Nashville. No one has ever complained about the quality or sound of the drums or the song.
     That being said, is the main difference between midi and drum loops just in the work flow, or is there something significant -- not something minor -- that is better about programming drums? The Drums on Demand sound fine to me. I'm just not going to ever get into any kind of serious programming because I don't like it and I'm not good at it. And, I like to keep things as simple as possible.
     And lastly, if I want some fancy drum track that I can't achieve with loops I can get some friends in Nashville to do them in their home studios pretty cheap and they sound great. Today, especially with the variety and quality of triggered drum sounds, plus having a real drummer, I just can't see why I would need to spend time trying to learn midi drum programming.
    So, for my purposes as described, is there any real advantage of midi and programming over loops?
    Thanks!
DS

Not if you have already decided that you would not benefit from there use. The reason that I like drum programs over loops is the ability to change the tones of the drums, by using different kits, or kit pieces to try to get close to how I imagine how I would like things to sound. You can not do the same with loops.

You're not wrong.  Drum loops are awesome and there is literally anything out there you could want to use.  But honestly the only real reason for programming your own drums is for the over all control you can get with each hit and each sound, and of course to say the line is your unique line, but if you're not interested in controlling every aspect of the drum line yourself then really there is no need to make it yourself.
 
I myself have not used drums loops too often because I like to mess around with the sounds and alter each hit and sound to fit my end goal, personally I use Session Drummer 3 cause it allows me to insert any drum hit I want and I do have a huge library of hits to choose from.  But I have, just this passed week starting looking into some of the many drum loops I also have and have been blown away with the ease of using them. 

not only that, you can adjust midi, say, to get the kick to sync to bass.

Thatsastrat
Not if you have already decided that you would not benefit from there use. The reason that I like drum programs over loops is the ability to change the tones of the drums, by using different kits, or kit pieces to try to get close to how I imagine how I would like things to sound. You can not do the same with loops.

Although now having Drum replacer altering loops in the same way is increasingly similar

I find EZD2 to be the best of both worlds.  Drag/drop in the EZD interface.  You never have to touch maps or PRV.  Plus you can tweak things inside EZD to balance levels for kit pieces and such.  That's if you use Toontrack MIDI, of course.
 

Drum loops can actually sound better than these programs as they allow for a level of articulation not possible with MIDI systems.  (see the program "Drum Core" for evidence of this they offer loops and the midi equivalent of thousands of grooves - recorded from the same source.  The loops are more detailed in what they can sound like).  
 
However loops offer a workflow where you are basically stuck with what it is and it needs to be within a few BPM of your project if you want it to stay sounding great.  
 
Using drum loops tends to dictate to you what you will do, not the other way around and for a lot of people that is limiting when they are trying to create their own work.
 
Try taking a drum loop and creating a verse, chorus, bridge with some variation throughout.  That takes quite a bit of work, and luck to match a song that you wrote without using the loops.  
 
Drum loops can be fun and easy if you just want a static groove to jam over, I like them for that.  But if you are trying to create your own piece, that is where the MIDI based drum programs can really shine.  

     I've got an older version of EZ Drummer and a fairly new one of Superior Drummer. I've played around with them but I never programmed one complete song with them. It was fun going in to the mixer and changing tones and volumes, and also it was fun changing drum kits on most all of them these days, but I'm just not a drum nut and I never got fascinated by the endless things you could do. All it did was confuse me with too many options and I spent most of my time just trying things out rather than actually programming a song.
     I've got a friend who tinkers around with this a lot and every time I ask him, "That sounds good. What drums are those?" it's always Drums on Demand. I guess my ear just likes them. And I never heard a song done with Drums on Demand that I thought could have been improved if someone had just used midi drums and programmed them, tuned each drum a little differently, added a tiny thing here or there.
     I have an engineer friend in Nashville who set up my Superior Drummer a few years ago. It may have been the best sounding DAW drums I've ever heard, but of course he makes stuff sound good for a living. I also realized that it wasn't so much the drum program but rather the slap-back-echo, and EQ and Reverb he put on them. Without that, they wouldn't have sounded as good as raw Drums on Demand.        
     We're starting to add those sort of effects more to Drums on Demand and I think they sound great. I don't know how we can improve on it much, if any. The only advantage I saw then, and see now, is once my engineer friend got them set, he made a template that opened with those same settings every time. I might could do that with loops, but I also wonder to get if right if I'd have to add the effects every time.
     For what I'm doing it doesn't sound like I'll be improving much, if any, by changing from loops to midi. And I know it will be a lot easier, at least for me. I had a solid state Line 6 amp a few years ago when they were coming out with all the presets and gadgets. It has so many controls and then deep menus of all these presets to get certain sounds. It would have taken me hours and days to have gone through all that. It had so many options and menus that it was confusing. As they say, it sparked more heat than light. I finally got rid of all the solid state stuff and went back to my old tube amps and life simplified immediately, and sounded better too. I'm guessing that would also apply to the infinite way you could program and set up midi drums and patterns.
     Thanks for the input guys! Very interesting insights.
DS
 

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Do the best of both worlds - Midi loops.  You don't have to program them, but you can interchange kit pieces, etc. to make them sound the way you want.