are these the ones that fit a strat but are way over wound?
with ceramic magnets they might not be muddy with a 250k volume. i'll bet they are designed to be a direct drop-in for a strat.
now that said i'm sure they will sound good with either choice. now if you want to try both and compare you can get the 500k and get a 500k resistor. the resistor will go from the #1 to the #3 lugs on the volume to give 250k.
the tone can be any value, well within reason, a 50k would be a bad choice, a higher # has a wider range, more treble when on 10. but that only goes so far, i doubt anything over 1 meg will be usefull. a high value will have a different taper, may have little effect in the first part of it's range.
i also came up with a clever way to get both volume pot choices using 500k pots on the volume and the tone, i do this on guitars with singles and humbuckers where both are desireable. if you don't want to add a resistor to your guitar and decide 500k isn't what you want you can do something similar.
