I forgot to try to answer your question... No, it won't change the sound of your guitar (that is if you use the same value's... 250K for single coil pups and 500K for humbuckers).
The A and B difference is the taper.
Let's say you have a 500K pot. if you turn it one way to the end the resitance is appr. 500K, turn it the other way (also to the stop on the pot), it's 0K.
A linear pot would measure 250K if you have the shaft of the pot in the middle, the taper is linear.
On a log. pot the value would be very different (400K or 80K..just an example to explain) if you turn it exactly halfway.
The pic explains: The line marked with R0 would be a linear pot, the line with R1K would be a log. pot.