sata 2 will give you only 2x the best hard drive speeds in sequential operations. Sata 3 gives 3x.
But, the os does mostly small random reads and writes which are 50x faster with either sata 2 or 3.
Everything you do will feel so much quicker.
As to brands, the reality is that all modern ssd's perform about the same.
My preference is Intel 730 or Samsung 840/850.
They both make their own nand chips so they can do a better job of validation.
My preference is Samsung. I like their free ssd migration utility.
They also offer a ssd cache software option called "rapid mode"
As to pro or evo, the pro will offer longer endurance. Your pro ssd is likely to last 15 years vs. 10 for the evo. A moot point, I think.