I'm one of the few people (to my knowledge) on the forum whose kid had both the SB-V and the WISC. DS6 had a horrible test day for the SB-V--lacking several hours of sleep, illness coming on, etc.--so he tested GT on the SB-V but not DYS-level, and it was clear even to the tester (who had just met him for the first time that day) that DS6 was not really showing what he could do. "He seems tired," the tester kept saying. He advised us to retest with the WISC to get a truer read. We did and we're glad we did.
Plus I'm not 100% convinced that the SB-V was a good test for our DS6. He showed verbal on the SB-V, which is supposed to be more geared to spatial kids, but he showed highly spatial on the WISC, which is supposed to be better for verbal kids. <shrug> Odd.
Anyway, the nice thing about the WISC, I think, is that it's shorter than the SB-V by a lot--like 2 hours shorter for us. That's a lot better for a younger child. Because it's shorter, it's also usually cheaper.
I think I'd recommend starting with the WISC for a younger child, even though this seems to be running contrary to some of the wisdom I'm hearing in this thread. But I also recognize that since the WISC is what got my son the good score, I may be unfairly biased in its favor...
