Funny, I actually own both of those basses.
Modulus VJ 4 that is rear-routed and with a highly figured top.
Bartolini pre-amp and pickups. 2005 model.
Warwick Thumb bolt-on 4 has all the original specs. 2003 model.
I tend to go back and for between them. Here are a few comparisons:
The Warwick pickups/pre-amp are FAR hotter. That being said, there is a HUGE volume difference. I find my Warwick has a sort of overdriven tone when played through my Eden WT-800 w/ 410XLT.
The Modulus neck is much faster, shorter, a bit wider, but less dense. Keyword: FASTER. The graphite has a completely different feel and is general quite cold, always sleek and, personally, I can play MUCH faster on it. The strings are spaced farther apart than with the Warwick, therefore making it easier to play slap.
The bodies are completely different. The Modulus is kind of an oversized jazz bass body, with a slightly heavy body but very light neck. The Warwick is small and heavy overall with a nice bit of neck dive. I prefer holding the Modulus as I find myself wearing the Warwick higher and sometimes angling it DOWNWARD a bit?
The Modulus tone can be quite tin-y. That being said, it is still very jazz bassy, much moreso than the Modulus. Which is funny because they both sport two jazz pickups. The Warwick tone is much fuller and really kicks in the lower mids and sometimes the highs (pending how you eq it). The Modulus I find is NEVER full sounding and requires a lot more eq for a solid THICK fingerstyle tone. However, the highs on it sing a lot better than the Warwick. I prefer the Modulus for slap and the Warwick for fingerstyle (if you don't mind it having a slower fretboard/neck).
Here is a funny thing I noticed. The Warwick knobs are farther away from the neck than with Modulus. I find this useful as with some strumming techniques I might accidently hit the volume knob of the Modulus if I get too aggressive/into-it.
Another small point. It takes a lot longer to change the battery with the Modulus as the plate requires a screwdriver and is slightly annoying to get off. This could be half annoying if the battery dies while playing live. However, you can easily avoid this by putting in a new battery for each show, pending the frequency of your gigs (this is what I do, I mean, batteries aren't THAT expensive). As well, the Warwick drains batteries a LOT quicker...if that matters.
In my opinion, the VJ aesthetics are far superior as well. But, this may be due to the maple top I have on mine...even though graphite necks look badass haha.
Overall, I find myself going back and forth. I used the Warwick live for a long time, then switched to the Modulus as my main gigging bass. However, I went back to the Warwick because I prefered the thicker tone and whatever slap I do live, I do on my fretless Stingray (w/piezo, of course!). As well, the voluem of the Warwick is much closer to the Stingray then the Modulus is. I actually need to have completely different settings on my amp if I use the Modulus at a gig whenever I switch between that and the Stingray. However, sometimes I can be vain and use the Modulus just because I know pictures are being taken (haha, at least I'm honest!).
Hope this helps!