How powerful is the engine, and how will you be driving it?
Even the diminutive and obviously semi-choked stock air cleaner will flow a reasonable volume of air for most needs.
Until you get into bigger power numbers, or always wanting that last bit of poop out of your right foot that is.
That's no real answer I know, but I'm thinking the 10" is fine unless you need more power than most. A 14" is more "typical" of what most people use I think, but I think too that they can handle 400-500 hp engines as well.
If you check out the YouTube video on air cleaner performance on the dyno that Engine Masters did (
https://www.youtube.com/watch?v=EkpsydS8JXI) you'll likely decide that while 10" is not quite as good as 14 is, pulling the top off and putting a salad bowl on top would be best!
It's actually a cool vid. As are most of theirs.
Paul