Pots of the same value will have the same output when maxed. However, there are few things to consider when choosing pots:
* Taper: two common tapers are linear and logarithmic and latter are used in 90% of guitars. Unlike linear pots, there are huge differences in logarithmic tapers between different manufacturers. True logarithmic curve is almost impossible to recreate, so different manufacturers use different approximations of the logarithmic curve. Now, why is this important to us? Because they will behave differently when pot is not
maxed. Better logarithmic taper will increase the volume steadily throughout the pot travel, while not so good ones will have sudden jumps (usually in 0-5 range) and dead spots (almost no change in volume when you move from 7 to 10 for instance). Good audio taper makes the volume pot much more useful, as I found when switched from ibanez (prestige) pots to bourns sealed pots. I found some chart that shows how big the difference can get
The bourns pot I mentioned is close to gibson pot on this chart (red line), note that at 50% of the travel it only reaches 10% of the resistance. That makes it very good for volume swells because it doesn't suddenly jump when turned from 0 to 1
* Tolerance: pot value tolerance is usually 20% which means that your 500K pot can easily measure 600K but also 400K. That can make the difference in output (bigger = louder) and tone (bigger = brighter), even between two pots of the same model. For consistent results, try to measure pots with the ohm meter (across outer lugs) and get ones that are closer to the expected value.
* Technology: there are two common technologies used these days - carbon composition (more common) and conductive plastic (more expensive). They both work fine, but carbon is supposed to wear out sooner and become noisy when the pot is turned.
* Power rating: although there's almost no current and power to speak of, bigger power rating is supposed to be less noisy. Usual ratings are between 0.1W to 0.5W or even better. Small 16mm pots usually don't have the power rating over 0.125W, so I'd use them only when there's no space to fit a proper 24mm pot.
* Case construction: there's an option of open and sealed pots. While former are much more common (due to cost), getting sealed pots is a good idea when swapping pots. They won't get scratchy because of the dust and won't require cleaning.
As far as switches go, differences between cheaper and expensive ones are more mechanical than sonic because they do nothing to the signal other than rout it from pickups to output or ground. Cheap ones will wear out sooner and they won't make as good contact as they should. That could result in low output, intermittent volume loss, noise, etc.
Hope it helps.