If ENT is any guide, the upper end of the Valiant's crew size was less than that of the NX-01 Enterprise.
Historically, the crew size of ships and combat vehicles or aircraft has gone down
with advances in technology...
No such trend in spacecraft yet, but then again, starships have precious little to do with today's spacecraft.
I'd like to see images of what the Valiant might have looked like.
Courtesy of Drex Files:
That's before the warp nacelles were added - but one might well speculate that this is what happened in the real world as well, and the surprisingly early launch date of the Valiant
is the result of the makers taking an already existing sublight spacecraft and just bolting on the newly invented FTL drive.