I've never driven or been in a car with the S1X, but I've owned both the XP and VS, and I can definitely say I like the VS more.
The XP felt flat down low, even with 3.29's and 9.4:1 compression. The VS, on the other hand, hits hard the second the pedal goes down and barely gives up anything on the top end, at least according to my butt dyno.
The XP is probably the faster cam on a highway pull, but I don't street race, so I don't care.Cruising around town and for quick WOT jaunts here and there, the VS feels GREAT. I think an intercooler on top of my current setup and I'll be all set, unless I come across a big pile of money and suddently find an intercooled 10:1 L67 with a Gen V, XPZ, and aluminum heads under my hood.
