I'm in the same boat as you OP, and the one I think I am dead set on is the Crucial M4. Even though the OCZ ones have faster read/write speeds, from what I have been told and what I have read up on these speeds are only marketing figures and in most cases with testing, the speeds did not live up to what was in the specification. Also, the OCZ use the SandForce SF controller which is known to have issues where BSOD's & read/white error's occur, resulting in RMA's.
From my research the Crucial M4 drives which use Marvell controllers have been shown to be much more reliable and durable, in some tests done the Crucial M4 has actually beaten OCZ Agility 3 SSD's in certain benchmark's. Lastly don't forget as well that with the Crucial M4 SSD's, you are getting 8GB more storage compared to the OCZ Agility 3 one (bearing in mind that usually the price of this one is £155, but at the moment it is £134 as it's on offer this week). I will also echo and agree with what others have already said on here, I would choose reliability over speed anyday.
Liam