Energy consumption, size and output strength mostly. T5 are "high output" and the fixtures tend to cost more. T8 are more common and the fixtures sometimes less expensive.
The benefit of T5 is that being stronger they can be placed further away, and are also visibly brighter. T8 are still good, and are easier to find at local stores usually.
taterbug i really appreciate youre taking the time and helping me out, i have a few more questions but will save them for when i'm home with everything there LOL. I just want to make sure what i have and plan on doing will be correct for sheldon.
Thanks!