the V3 has internal jumpers to set a -20dB attenuation.
Perhaps those jumpers were on the whole time you were running the V3, so you needed an extra 20dB from the pre-amp to make up for the input attenuation. Now that you are running the V2 without the -20dB input attenuation, the gain needed is 20dB less.
and, as eric.B says, the output levels are slightly different.
From the V3, the balanced XLR outputs max out at +25dBu.
but that's only a couple of dB different from the V2 outputs (assuming what eric.B posted is correct - I didn't double-check what he posted), so that wouldn't account for the large difference in gain needed.
While my first thought is just a guess, and I don't think there's any way you can verify it (unless you still have the V3), I think its the most reasonable explanantion.