I've both with all bass related stuff on both.
As I sees it:
The SVT Blue line on Jamup and the SVT CL on Ampkit are so so close to each other. The Anpkit unit is maybe a tiny bit more versatile as the Ampkit SVT is a CL, 8x10 cabanas several mics.
The Sansamp BDDI in Jamup is great, but so is the Sansamp GT2 in Ampkit. Otherwise, the Orange AD200, SWR Redhead, the two GK's, the Acoustic and the Fender Super Bassman are better then the Trace Eliot the Fender bassman and the Ashdown in Ampkit.
Jamup is the best bass amp sim out there, Ampkit comes a respectable 2nd while Amplitube is outdated. The only solid point of Amplitube is superior recorder/ studio but I use Auria and Cubasis for recording.
Yeah I bought amplitube ages ago and never use it. It's got a nice chorus pedal and that's it! . I've got auria and cubasis too. Amplitube sucks !
Thank you for the insight. Maybe worthwhile while its on offer!