I have driven both, VZ exec and BA xt, the BA's are pretty much a full second faster 0-100 than the VZ.
But it's not only the WOT squirts where the BA has the goods, at partial throttle applications the BA effortlessly pulls it's weight along to keep up with or better the speed of the other traffic from the lights, while the VZ needs a fair bit more of a kick in the pants to acheive the same, unlike the previous ecotec which was fairly responsive at partial throttle openings.
I found the VZ exec a little dissapointing, reminded me of a bit of a jap V6 having nothing down low in the revs but not a bad top end, but I haven't driven an SV6 yet but I'd imagine in the lower revs it'd be exactly the same but with a stronger top end.