I agree GRs interface is much easier to work with however TH2s sound is much better IMO. More realistic and the few amps that came with the Producer version (the lite version) are extremely versatile once you get to know how to use them.
A couple notes on both programs.
In GR the Hot Solo head is the best/most realistic sounding for most rock/blues/metal/punk type stuff. If you end up getting the upgrade to GR 5 ALWAYS use the Control Room Pro option for your cabinet (not the regular Control Room... use the Pro version). Mess around with different cabs and mics as well as the mic placement on the cones (you get three options for mic placement in CRP). ALWAYS use the "Hi" setting at the top right of the GR window. It uses more computer resources but the quality is much better. Google Craig Anderton's article at SOS about working with guitar sims. It will help you eliminate some of the sim harshness (you can apply those principals to any sim). There is also a section where he shows this procedure in his X1 videos if you happened to purchase them (or got them as a freebie like I did). Make absolutely sure the In/Out levels within GR (including the cabinet section) aren't peaking as well as the tracks/busses/PC strip you are sending it out to. That means play as hard as you can while setting these levels. That way when you play normally you should stay within appropriate levels. I find the best way to do this is to wail on a full six string G chord in first position as it seems to create the loudest output of everything I've tried but also try other chords and squeals, etc...
In TH2... seriously read the manual. It is next to impossible to figure out all the critical features in TH2 without knowing how to access them. For example, you have to click on the cabinet to get access to all the really intense settings like mic placement and IRs. On the heads try the Variphire knob (it's that weird looking red thing that sticks out the side of the head). I'm not sure I understand exactly what it's supposed to be doing but it adds a LOT more depth to the sound. Supposedly some weird proprietary coding to mess with the signal in a pleasant manner. Also use the blending fader on the amp heads. You get two separate models on those heads and moving that fader between the two changes the sound drastically in most cases. It's also not like the usual blending option you see with dual channel hardware heads or other software effects. Like the Variphire they did something weird to the code so it actually BLENDS as opposed to acting as a volume fader between the two. Check out different amp models together while playing with that fader. You'll see it's pretty intense. The bank saving system is kind of arse. I've personally just been saving my presets by a) typing in a name in the normal preset name box then b) pressing the little floppy disk Save icon. Just like you would save presets on the other stuff in Sonar. Unless you are using TH2 as a standalone for live stuff this way is far less annoying and easier to recall your setting from IMO. Try out moving the modules around in different orders. The sound difference is huge. I find setting things up like I would my guitars, amps and pedals in a real life setting is usually the easiest way to go. Some of the presets put the pedals in weird places in the line and it's not so great once you deviate from the initial settings so yeah... set things up like you would in real life. However try out different configurations because sometimes you'll strike gold. To insert modules into places they don't seem to have a slot for already you have to click on the patch cable. That one took me whining to the forum to figure out and scook showed me. I don't think it's even in the manual. Again look at the Anderton tuts on working with amp sims but I found with TH2 it wasn't nearly as needed and I only did some of the stuff in that tut and not as drastically as I would with GR.
Anyway... that's all I can think of for now and I need some tea since I essentially woke up and started typing this. lol
Hope it helps some folks.