how much difference will 1 extra tooth on rear make

switching out chain & sprockets, got a silver JT chain, oem front and two rear sprockets. One is an old (unused) silver 48T and the other a black prox 47T. I would prefer to use the black sprocket as it looks way better on black warp9 SM rims, however if there is a significant difference in acceleration with the 48T I'll fit that. not the greatest dilemma I know

It would be noticeable, but not a huge difference.
I'd try it and see how you like it.

When I rode a WR250X, my sprockets were 13/49.

Yeah its probably best if i give them both a try. Thing is it was an absolute nightmare removing the old torx bolts, which had the metal type lock nuts and loads of blue loctite. The old sprocket had been on the bike for 4/5 years and ridden in all sorts of weather. The proximity of nuts/spokes made it nigh on impossible to loosen nuts. i ended up snapping 2 torx heads and eventually had to weld on a bolt and get a breaker bar to get the f=cker off!

i have a new set of bolts with nylock nuts, should i use loctite? And apparently nylock nuts lose their 'strength' every time they are tightened/loosened??