Since Sonic Synth is new (and also distributed by IK Multimedia as well FYI) there will be more and more users around who can offer their opinions as it becomes available in the stores shortly. Perhaps someone who has these two will catch this thread and post right here as well.
If you or anyone else REALLY wants to know about how Sonic Synth compares to XL's sounds or other VSTi products for that matter, you can read user reviews here: Also, you can read info and listen for yourself with downloadable mp3 demo riffs of about 100 Sonic Synth sounds here: There's even some free ST (and other sampler format) sounds from us from (you would need a commercial Sampletank to playback the free sounds though- currently ST FREE does not work with them but that will also change soon ). Second, my personal career in music tech began 20 years ago in 1993 with the release of Typhoon for the Yamaha TX16W sampler. First, it marks the tenth year with Sonic Charge and Microtonic (happy birthday little drummer boy). I know that Rabid who frequents this forum has it and so does David Bryce (although I am not sure if those guys also have Sampletank XL to compare). 2013 is drawing near its end and it is a special year for us. The ST engine is a good one to have especially with the cool eROMs around (I have symphony strings). I personally tend to use the pads, synths, pianos, organs, ethnic instruments and basses the most. As far as which is better well.that should be for a user to say since I am the main person who made Sonic Synth's sound content. Sonic Synth is by far the 1 instrument in my studio. You do get more sounds with Sonic Synth for less money though. I think both are very good and worth the money.