I am looking into a new build and i was wondering if 4 256 GB ssd's in a raid 0 would give better performance than 2 512 GB ssd's in raid 0. Also the ssd's i am looking at are Samsung 840 pro's are they the best? I would primarily use them for gaming/3d rendering.
Don't bother raid 0 with SSD becuase they do that anyways. Note how larger SSD's tend to be much quicker, especially in the writes. The main speed advantage of SSD's is their virtually zero access time, that is, it can switch from file to file instantly while HDD's have to move the head and spin the platters to get there. All that Raid 0 will do is increase the throughput, but a good SDD will nearly saturate a SATA 3 interface. Having a massive throughput of raid 0 SSD's will only help with server/simulation type issues, not with loading games and booting up the PC.
For one TB of SSD, go with Samsung's new 840 EVO. They have a 1TB one, it is fast as blazes and cheap.