I'm rather new to using DAWs and I'm currently using the trial version of X2 while waiting for my purchased box to arrive. 
Prior to purchasing X2, I had been using another DAW and had purchased Ez Drummer. I'm wondering if Session Drummer is equivalent to Ez Drummer and or is Ez Drummer a superior product to Session Drummer or are they just different?  I've not yet had a chance to use Session Drummer as I'm still trying to get my head wrapped around all the other functionality that X2 has to offer up.

Anyway, thanks for the help.

I prefer using ez-drummer, I can't really comment on session drummer 3 as I only have session drummer 2. I find the ez-drummer software sounds better though.

In my opinion EZ Drummer is far superior to SD3, especially with expansion packs.
 
I'm not slagging off SD3, I think it's okay and very good for a bundled piece of software.  I still use it for a few things.
 
I think EZ Drummer, and it's bigger brother Superior Drummer are excellent.

EZ Drummer will serve you well. Session Drummer 3 is a good bare bones drum sample player with good sounding drum samples and the ability to get more but its a simple drum synth that EZ Drummer can beat easly. 

I use Battery 3 and BFD2 and have only used SD 3 a few times. Its OK for quick work but if you want the power that a great drum sampler can provide it wont compete. 

I'm a big fan of Session Drummer 3. Paired with the Step Sequencer, it's very powerful. You can drag your own samples in to Session Drummer and create your own custom kits. SD3 is a 12 track/output sampler so you can route up to 12 drums/samples to individual audio outputs (these show up as tracks in Sonar), and add effects to each individual output.

Not sure how all that works with EZ Drummer. I've never used it.

Another thing to keep in mind is, I checked EZ Drummers site, and they said you have to have Version 8 or higher to work with Sonar X2. You may want to check which version you have.

There is a 3 part tutorial for using Session Drummer 3 on Youtube. Do a search for "sonar master class drum production". The difference between these tutorials that were done for Sonar 8.5 and what you will see in X2 is, there are Track Templates in X2 that are already set up so you don't have to manually create the audio outputs like they show in the video ... but it's still good to know how to do it.

+1 for Toontrack - I use Ezdrummer with the expansions (I have 8) and then Superior when I'm finishing & ready to bounce it down - the expansions all work with Superior Drummer too - My 2 cents

both

I use both of them in X2a.  EZ Drummer's interface makes it easy and fast to try a lot of patterns out at tempo.  When you turn it on you have every pattern in your library (1,000's) at your fingertips to try out.  With SD you have to load the patterns into a 8 part grid.  If you don't have what you want, load some more.  It works but it's very time consuming. 
 
SD has a lot of nice sounding kits.  I wish it had an organized pattern browser like EZD (hint, hint).

Neither. XLN's Addictive Drums knocks both into a cocked hat (IMHO)   ;O)

I do not use the MIDI pads in SD3 for auditioning loops. The MIDI loop browser in SONAR works just fine for auditioning drum loops. The MIDI pads can be an interesting way to play loops in realtime to create a drum track.