I have a sata2 motherboard: is it worth to buy a sata3 ssd or I should stick with sata2?

I have a sata2 motherboard: is it worth to buy a sata3 ssd or I should stick with sata2?

I have a Gigabyte Motherboard ga-p55-ud5 (sata2 controller) and I plan to buy an ssd disk.
Is it worth to choose a sata3 disk (like the vertex4 128gb, just to say one) or it'll be not fully used by my sata2 controller and I'd better spend money on a slower sata2 ssd disk (but with more space like a samsung 250gb 840 ssd basic)?
I'd be sorry to spend the same money,