OCZ has a custom firmware, they have an exclusive type deal with Sandforce. So in theory it should be faster, even if just.
ADATA, Patriot and Corsair probably ship the bog standard Sandforce firmware. Which doesn't make it bad, they are awesome, but at the same price point or R100 less, I would opt for the OCZ instead.
Patriot, OCZ, ADATA and Corsair SATA-6G SSDs available locally are all Sandforce 2 SSDs. The main chip isn't different between them. The difference comes in with the NAND flash type they use. OCZ does however have a exclusive relationship to get their updates from Sandforce first.
Performance wise:
Toggle nand > Synch nand > Asynch nand
You would be hard-pressed to notice the difference in performance however. You need a benchmark to tell the difference (and it isn't huge).
OCZ Agility 3, Patriot Pyro, ADATA S510 = asynchronous NAND
OCZ Vertex 3, ADATA S511, Corsair Force 3 = synchronous NAND
OCZ Vertex 3 MAX IOPS, Patriot Wildfire = toggle NAND
Once again, all of these use the same Sandforce 2 controller, only the type of NAND is different.