A lot (most?) people shooting long range and/or the long spiky VLD-ish bullets from a 6.5 whatever seem to tend to go w/ an 8 or *maybe* an 8.5 if its a hot rod. I think the 9 is more common on hunting rifles, carbines, etc. where extensive use of long 140+gr VLD's isn't really expected. That said, there are some 140gr 'hunting' bullets like the 140 SST from Hornady that are pretty VLD-ish in ballistics! I don't think (based on the use of 107/108 and 120/123gr bullets in competition by myself and a lot of others) that the lighter bullets are going to be adversely affected much by the slightly faster twist. It's not like going from a 1-14" to a 1-6.5" in a .224 caliber; not near as drastic a change. I'd err on the slightly fast side to make dang sure you are able to stabilize the heavy bullets; the lighter ones will most likely shoot just fine.
YMMV,
Monte