Whats the difference between t5 and t8 lighting?

The difference between T5 and T8 floro's is the bulb and ballast. T5's are physically thinner but spit out more lumens, they are better then t8's. i think they create more then double the light.

I am not sure on the difference, but I use the t8's for vegging and they work great. I found them on ebay too. I am no lighting expert, but I have been happy with them.

Basically, the number after the T is the numerator for the fraction based on T8's being one inch. A T12 is 12/8" or 1.5 inch diameter and T5 is 5/8".
In spite of what dmxcrew says, one isn't 'better' than another. There are different lamps for different purposes, sizes, wattages, etc.
The light efficiency goes up with the thinner bulbs, more lumens per watt, but there's more to it than that. There are HO (high output) and VHO (very high output) T8 and HO T5 lamps. Those higher wattage lamps need special ballasts, run hotter and less energy efficient but the increased wattage gives more overall lumen output. So it's not a simple matter of just comparing size.

Since extreme light intensity isn't going to be a requirement for clones or keeping mothers, T8, T8HO and even T12 can be used. If you can get a nice T8HO setup for vegging (I found a 4 bulb Silverstar on eBay for under $90 shipped), you can use an inexpensive NO T8 from Lowes ($40) for your clones.

Also look for fixtures using biax lamps. Those are compact fluorescent but not the ones you are thinking about. These are 24" 55-65w dual tubes (like a 4ft T5 bent in half), vary narrow (36" lengths are 96w each for 192w total in fixture a foot shorter than shoplights). So you can fit 2 side by side for 110w in a good reflector with a 24"x6" footprint. Great for clones. Here's an example of a dual 55w http://www.htgsupply.com/viewproduct...roductID=51907