For me BIAS FX is a hole 'nother level to S-Gear 2, I haven't touched S-Gear 2 since getting BIAS Amp Pro and then BIAS FX Pro when they came out, I would also through TH2 Full above S Gear, when you spend enough time understanding how it works, how to get the most out of it, it really is a gem as a lot of folk have found. I have always been able to get better sounds (to my ears) easily out of TH2 than S-Gear 2, plus TH2 has the works, almost everything you could desire, and all top quality. While good, I have always felt S Gear 2 to be over rated, I tried using it quite a few times after my initial 'WoW' when I first heard it, used it, but not once kept it in the mix, always replacing it with TH2, and now BIAS Amp/FX as well.
IMO you would be crazy not to get BIAS FX and put it through it's paces for as long as it allows before committing to purchase
any other amp sim.
Oh, and for all your distortion needs, don't forget 'BIAS Pedal' is being released tomorrow, I have been using this for a while as part of the explorer program, AWESOME, again you will need to learn/understand it to get the maximum, but straight out of the gate it is pretty inspiring
As with everything, this is just my opinion, and it all depends on your 'bent', what you are into bla bla bla, so YMMV