There is ONE disadvantage to tsop flashing.
If you have a 1.2-1.5 xbox you are limited to 256k bioses, whereas most chips have 1mb, allowing you to use multiple bioses. If you have a early model xbox, hook up a switch have one original bios, and one modded bios. Note that you will only want an original bios if you care about live.
If you dont care about xbox live, then tsop flash the thing and dont even look back. there is no disadvantage to a proper tsop flash.