From reading reviews and forum posts most suitable ssd would be Samsung but I'm not sure if high price is worth it. Performance/price wise best choice would be Agility 4, is it really that unreliable and are there statistics that really shows that? Or should I just go with one of in $240-$260 range. Oh, it will be my first SSD and primary usage is for gaming. Cheers!
The M4 is getting a bit dated, but it still a solid SSD which has been proven over time. Definitely don't go with the Agility 4. It uses cheaper NAND which causes a severe write performance hit due to the Indilinx controller lacking the same sort of compression technology that SandForce had. The Vertex 4 is fine, but for an average user, it may be better to go with a more reliable option like the Samsung 830 or Crucial M4. The Samsung 830 is a very solid drive, which I'd take in a heartbeat if cost was no object. The Plextor M5S doesn't look like anything special compared to the old M3 that it replaces. I'd probably take the M4 overall, but if you do want to shell out the money, the Samsung 830 is a better (and equally reliable) drive.
I personally would go for the Vertex 4. The 830 is fairly good as well, but wouldn't go for the Crucial M4 as its a bit old now.
Would avoid the Agility, its OCZ mid-range product and doesnt perform as well as the others listed. Great choice if pure $/GB is the goal.
Dont know enough about the Plextor M5S to make judgement.
Vertex 4 has some firmware updates on it that improve performance. You dont need to constantly update though, mines still running 1.4. Just update it when you get it and leave it at that.
Not sure about the 830, but I would assume it has had firmware updates.