Hey Jules
Compared to the TI, the Virus B is missing these aspects:-
Oscillators:
• Hypersaw (upto 9 detuned saw/squares using one-note of poly)
• Wavetables (I think at release the TI had 72 wavetable PCMs to choose from but more may have been added since then.)
• Wavetable PWM
• Graintables
• Formants
Polyphony
• Up to 80 voices (as opposed to 24 of the Virus B)
Filters:
• Moog 1/2/3/4/5/6 poles
• 3 band (inc. parametric Mid) EQ per part
Modulation
• 6 slots (each 1 source + 3 destinations = 6 sources + 18 destinations in total) as opposed to the Virus B's 3 slots (with 3 sources and 6 destinations in total).
Arpeggiator
• User programmable
Total Integration
• Virus Control
• 3 stereo USB outputs (at 16-bit 44.1KHz only)
• USB MIDI
• Searchable categories/sounds
• "Section locking" (ability to mix/match different parts of a patch with other patches).
Misc
• 17+ ROM banks (compared to 8 of the Virus B)
• 3 user-definable "soft knobs" (compared the Virus B's 2)
Outputs
• 6 x Balanced 24-bit 192KHz audio outputs on 1/4" TRS jacks (as opposed to the Virus B's Unbalanced 18-bit audio outputs on 1/4" TS jacks)
• 1 pair of S/PDIF input and output on RCA jacks
It's entirely a personal decision as to whether the differences would be worth the extra outlay, but hopefully the above may help either way. To sum up, the biggest audible differences would be in the new oscillators, and the Moog filters. The rest is effectively an increased feature set and for better workflow.