It's another product on it's own basically, it does compliment BIAS desktop, I was quite happy to pay the $199 ($270 AU) for BIAS FX Pro, well worth it.
I'm very happy with BIAS Desktop Pro and Bias FX Pro, the amount of quality amps and effects you get with BIAS FX Pro (Pro 60 amps 52 effects) is well worth it, and the sound is gorgeous, those lower gain/Fender Plexi etc, (
and not just Fender) type sounds I mentioned above, blow away S-Gear in my opinion, so sweet, and some of the High Gain stuff is just awesome, cleans can be deliciously sparkling or as thick as you like. I think it is an excellent compliment to BIAS Desktop Pro
S- Gear is most certainly not better, not in my eyes and ears anyway. I haven't touched it in quite a while preferring stuff like BIAS Pro, Recabinet 4, Vandal, TSE, (even regained my appreciation for Revalver, albeit 3.5 over 4) and of course my long time go to TH2. For me S-Gear has pretty much been relegated to the back seat with the likes of Amplitube and Guitar Rig, just don't get the urge to fire them up, and that in itself is telling.
But I guess things sound/feel/suit each individual differently, good to have choice though, as long as you are happy with what you got and use, others opinions really don't mean diddly.