Thanks for the comments, Kenny.
It depends on what the PC is being used for regarding sequential performance. For an OS, it doesn't matter much, but for something like video editing, then sequential performance does matter.
The "speed degradation after heavy use" tests is not testing NAND write cycles. At 3.66TB, the NAND life still remains at 100%.
The test is seeing how effective the SSDs garbage collection is working.
The Agility 4 has asynchronous MLC NAND. MLC NAND once it has been written to once needs to be read/modified before it can be written to again.
Asynchronous NAND can only do one transaction per cycle, whereas Synchronous NAND can do two transactions per cycle.
What the test does show is. sync NAND SSDs such as the Vertex 4 can clean the NAND faster than the Agility 4 which has async NAND, hwen both SSDs use the same SSD controller.