I would just go with the onboard wifi the RP3 has already as it works very well. Some of the chips inside USB wfi sticks are very cheap and nasty. They work fine to give you an network connection but they are not very good for use as an AP, how many people will be using them for a pirate box setup.
With the FCC trying to prevent changing the firmware in AP boxes off the shelf it looks like the RP3 will be the SOC board of ALL Hacktivists anyway.
With the FCC trying to prevent changing the firmware in AP boxes off the shelf it looks like the RP3 will be the SOC board of ALL Hacktivists anyway.