Clip on:

Pro: Cheap, can be carried on when buying new glasses
Con: you have to carry it separately, depending on the "system" (clamp, magnetic) they might Not be fitting when buying new glasses

Extra glasses (with correction)

Pro: Its Just the Same as the normal glasses but with sun protection
Con: you have to carry it separately, when eyesight Changes you need new ones

Sunglasses you can wear over your normal glasses:

Pro: relatively Cheap
Con: you have to carry it separately, bulky, only fits when you have relatively small normal glasses

Transition:

Pro: you only have one pair Con: they normally dont Work when driving a car because windshield Filters Most UV (which triggers the darkening of the glasses)

First three are First Hand experience from me. Never Had Transitions because i mostly need sunglasses when driving.