Scott - the VTs ARE available with a DI mod through Putnam (in case you weren't aware):
[Invalid or Expired Link Removed]
I personally have no experience with this, but I've read quite a few responses on here from guys who have had the mod done and they seemed happy. Also (if you are not aware, or are aware but perhaps it's more than you're looking for) the VT Deluxe is equipped with an XLR out:
http://www.sweetwater.com/store/detail/SACSVTDlx
I own both the VT and the Hartke Bass Attack. Both are really capable tools that have some tone overlap, and also some different features.
I use them for two different setups. In my main band, I play a Jazz bass through the VT into a Tone Hammer. The Tone Hammer rounds out some of the bright clack and boominess that the VT can produce. The dials are pretty sensitive, and it can be tough finding just the right EQ settings. To be honest, even though I really love the VT now, I didn't love it until I paired it with the Tone Hammer (just my experience, YMMV). In addition, you will see a lot of love for the VT on here using as an SVT type tone, but you will also see a lot of negative comments about its high drive settings and sweeping the Character knob too high. To me, its sweet spot is somewhere in between - punchy with just a hair of attack and grind on the top.
The Hartke is my at-home and side project (punk rock) setup. I play a Jag into the Hartke and nothing else. The Hartke can cop an aggressive Ampeg-esque grind, but on its most extreme settings (to me) it starts to sound fake. I use this mainly for a modern sounding pick tone. The benefit of the Hartke over the VT is its blend mode. The Hartke at its lower price, already equipped with the DI and a blend mode to boot is a very good choice as well (I've been extremely happy with mine).
Both pedals are a set and forget situation. If you were looking for a stomp effect, you should look elsewhere, as both impart too much of their own flavor to kick on spontaneously without having the tone change drastically.