I have Amplitube 3, Guitar Rig 5, TH2, and Kuassa. For my taste, none of them sound as good JamUp / Bias.
That said, I haven't tried the Orange pack, or any of the specialty packs. I did also buy the iOS version of Amplitube and it was truly terrible.
I know it's all subjective, so I expect I may be in the minority here, but that was my conclusion after many, MANY (dozens... hundreds?), hours of playing and tweaking.