I've used the VT Deluxe, YYZ and now use the DI-2112. I liked VT alot; however the DI-2112 has the features that I've always wanted but was never available in a pedal format.
The tone shaping options on the 2112 are really good - like the clean blend on the drive channel, deep channel w/saturation (to me acts for like an EQ filter), and ability to combine using the internal swith to put it all on one channel/out.
Clean blends work great retaining the original tone; if the the pedal settings are changing the original tone too much - just mix it back in (for me my USA MM Sterling 5 seems to loose it's tone if the original tone can't be mixed back in). My passive P-bass doesn't loose as much, so I don't blend too much back in. The YYZ sound best on passive basses IMO due to it not having the clean blend.