and being the owner of Superior...should I have an interest in the other?  I'm not looking for MORE...but is it *better*.
 
Just saw a video on FB that the guy says it slams Superior...you get all these extra drums without buying expansions, the layering is great and easy to do and then he raved about the cymbals and HH.

I like Superior quite a bit, but always have the door open for improvement.  Quite frankly, Superior done *right*...whatever that means... would seem hard to beat in the "sound catagory".    

They are both very good and both very useful. SD2 allows you much more control. Slate is "rock ready".

I have Slate and Superior, I rarely use Slate but it sounds good straight out of the box, so if you are not into a lot of tweaking you may prefer it. I don't like the interface. You can get a wider range of sounds out of Superior if you work at it.
 
If you are looking for "better", at the moment BFD3 is the "state of the art" in my opinion. The factory kits are the business.
 

I'd rather tweak...and I hear Superior is superior in that regard.  I don't need toms that already have room ambiance already locked in.... or something similar.
With all the EZD2 hype... Superior 3 can't be far behind either.   Gotta love those NY expansions.  I have a couple minor nits with the program and what I tend to think would improve it, but I'm just glad it exists and I don't have to use my Roland GM set anymore!

Is there any truth that BFD3 is a little glitchy?  Other than load times, Toontrack has always been solid.  Sometimes I have to reload, but not much.
 

mixmkr
Is there any truth that BFD3 is a little glitchy?  Other than load times, Toontrack has always been solid.  Sometimes I have to reload, but not much.
 

I have not encountered any problems with BFD3.

If load times are a problem, move the samples to a SSD. It makes a big difference.

Try out the Steve Slate preset pack for SD2. It makes Superior sound like Steve Slate's EX pack and it doesn't cost much.

https://www.toontrack.com/products.asp?item=66

Not exactly the combination that you are looking for mixmkr, but I have Slate, EZD and AD.  Slate is definitely the most rock ready of the 3.  It is tuned and processed for rock and as mentioned, I don't have to do much fiddling with it to sound like it fits the song.  I choose it, most of the time for my rock oriented songs. 

I use Superior more than anything else but I have to have the tweakability factor for a wide variety of styles. The load time is horrendous for live work. Maybe I will do as suggested and get an SSD. The Slate drums I have used in other studios and while impressive just doesn't cover as many bases for me as Superior. They also seem overly processed in the raw samples as well. I also own Addictive Drums and BFD Eco. Addictive finds its way into my live rig simply because it loads in a matter of seconds and is quite versatile as well. BFD Eco has sparked my interest in the full package. The BFD drums are very raw and authentic sounding for your retro old school drum sounds. I still prefer Superior. With the NY kits and the Nashville kit you can do just about anything you want. Also the latin percussion library for seasoning. LOL!