T5's have some advantages over T12s. They are more energy efficient because of their reflectors. T12s are hard to use a reflector with because of their size. They have a sort of built in reflector in the bulb. T5s are supposed to last longer than T12s. Depending on who you talk to T5 need to be replaced every 1-2 yrs. T12s should be replaced every 6 months.

All of them can be used for SW. It just depends on what you are trying to do with the tank. It all comes down to lumens and watts.