Both M3 and M4 have similar read speeds performance but the only difference is the price and low write latency of Toggle NAND by M3; which is important for databases with heavy write activity or workload.
Plextor M3 is in the price range of Vertex 4 and is limited to 200 writes per second.
Vertex 4 is more preferable choice for video editing with 400 writes per second.
Vertex 4 read performance is below M3 and M4 due to latency but the difference may not be noticeable by the average users.
Casual users that want to use a SSD for it's read potential with medium write workload then M4 is the ideal price per performance with reliability but different MTFB and Warranty. (MTBF is Mean Time Between Failures)
M4 with MTBF of 1.2 million is 160gb per day for 3 years warranty. (£83) (Write potential is more than 1029 TiB x2 from M4 64GB results)
M3 with MTBF of 1.5 million is 50gb per day for 5 years warranty. (£107) (No data on endurance tests)
V4 with MTBF of 2.0 million is 66.7gb per day for 5 years warranty. (£110) (The write potential is 390TiB with 1.4R but not tested with 1.4 final.)
The SSD warranty is based on the MWI (Media Wear Indicator) from S.M.A,R.T from 100 to 0. (CrystalDiskInfo)
After the MWI expires then warranty also expires but the SSD lifespan continues after the count and up to the SSD's potential endurance (Wear Leveling Count) within the 3000 writes per cell cycle and 4kb or 8kb page per cell.
Example: Assuming a SSD manufacturer provides 5 year warranty but sets the WMI limit to 90 TiB of wrtitten data and the user uses that amount in a year then the 5 warranty expires in 1 year.
Updated.Edited by tumbirs - 6/16/12 at 2:08am