Originally Posted by
Atlas Shrugged
There is no speed difference if you went with a supple 38mm tire which would be my advice. Panaracer GravelKing slick or Rene Herse, but there are plenty of options. No advantage to going 32mm.
This.
If your 'gravel' is really just smooth-ish dirt roads, and you don't regularly ride in mud and other nasty conditions, then a smooth 38-40mm tire will be perfect.