I'm contemplating purchasing Superior Drummer 2.  I currently have EZDrummer 2 and various kits for it.
 
I know that you can load the EZdrummer kits into Superior.  My question is this:  what additional functionality do you have in SD2 particularly with regard to the mixer?  
 
In other words, do you gain much by loading the EZdrummer kits into SD 2?
 
Note:  My overall choices are:  (1) get SD2, (2) get the BFD3 upgrade from Eco, or (3) just learn more of what I have.

I have used Superior 2 for years now. I have a number of the EZX kits that I used quite a bit in SD2. You do gain a lot more features to the mixer functions. The EQ is much better, compressor seems more polished, everything that is available on the mixer in SD2 kits is available to you in the EZXs. I have Addictive Drums 2 and BFD and I have to say, even as old as SD2 is, it still is my goto drum program. The only drawback I have found is the EZX kits samples have to be on the main drive, and I don't know if it has anything to do with it but the EZX Kits are slower to load samples than the SD2 kits.
Besides, if you already know EZ Drummer pretty well, you're half way there with SD2!! LOL!!!!

Sidroe
The only drawback I have found is the EZX kits samples have to be on the main drive, 

That is only a function of the installer. Most people did not realize that you had the option to install elsewhere and just clicked thru the (somewhat obtuse) option.
 
Now here's the downside. Unlike SD2 you *cannot* just move the libraries since there is no facility in EZD2 to declare where the libs are. 
 
In order to have the samples on another drive you *must* reinstall from the ground up all the EZD libs. I did that back when I migrated from XP to Win 7. 

My EZDrummer libraries currently reside on the (external) drive where I would install the Superior Kits.  So, that would mean I'd be okay, right?

bapu

Sidroe
The only drawback I have found is the EZX kits samples have to be on the main drive, 

That is only a function of the installer. Most people did not realize that you had the option to install elsewhere and just clicked thru the (somewhat obtuse) option.

Even if they are installed on the system drive, it is easy enough to use mklink to move Toontrack folders to another drive.

In case anyone has the same question in the future, I discovered that Groove3 has an entire video series comparing EzDrummer and Superior Drummer.  It points out what can be done in both programs and what can be done in only one.  It also shows many tips like "If you change this level in Ez Drummer, then here is what you'd have to change in Superior to do the same thing." 
 
I came away from the videos thinking, "Toontrack really has an odd pair of programs." Superior gives you lots of extra control but EzDrummer allows you to do some pretty neat things with one knob that require lots of adjustments in Superior (and some things you can't do at all).  I'm still on the fence, but I've got a month to decide.
 
One thing the videos do is really show the comparison between the mixers of the two programs so that was very helpful.
 
Thanks for the replies in this thread as well!

EZ will get you pleasant results very quickly, because that's what it was designed to do. Of course, quick 'n easy always necessitates some compromises. There's a reason race cars don't have automatic transmissions.
 
SD is much closer to the process of mixing real drums. It makes no assumptions about what you want your drums to ultimately sound like, other than that you probably want them to sound natural. Consequently, you have gobs of options for tuning even the smallest detail.
 
There's a reason EZ kits are half the price of SD kits: they contain half as much information. Surprisingly, this isn't as big a limitation as you might think. It mainly means you can't control microphone bleed like you can in SD2. That does compromise realism a little bit, but most folks won't notice.

I have both EZ2 and SD2, plus all EZXs and SDXs they make. I have mixed "completed" songs using one or the other. I have never used an EZX in SD2.
 

The main reason I got EZXs to work in Superior was I needed Latin Percussion along with a drumkit on 99% of the projects. It worked well enough to get me interested in EZXs. I used to do a lot of jazz guitar gigs for happy hours, weddings, etc. so the Jazz Kit by Futureman Wooten fills the bill very nicely for that small tight combo sound. The Nashville Kit with Harry Stinson still gets used a bit here and there. It works in just about everything but metal and the brushes in there are very good. I bought a few more just out of curiousity.
I have some of the SDXs but I have to say since I bought New York Studios Vol.3, I have used nothing else!!! Those kits are the top of the line for me. And the addition of the Plate Reverb in Vol. 3 is the best addition to Superior in a long time.

I upgraded from EZD to Superior Drummer as well.
I had access to the EZD kits through SD, but other than the Latin Percussion, I never bothered with them.  The SD kits sounded better than the EZD ones.