While the two drives look essentially the same, share the support for the SATA 3 (6Gbps) standard and have a 2.5-inch, 9.5mm standard design, the M3 is not really the next straight step from the M2, but rather a totally different step.
This is because the new drive is actually slightly slower than the previous model, which, by the way, is still one of the fastest on the market. To make up for this, the M3 is now much more affordable, costing just around $1.40 per gigabyte, compared to the current $1.80 per gigabyte of its predecessors.
The Plextor M3 is not in any way a slow SSD, however; it performed about the same as many other SATA 3-based SSDs, even faster than some, in my testing. It does seems to fit into a new trend of SSDs that trade a little bit of performance for a much more friendly price. This is good since to most users, moving from regular hard drives, these SSDs offer basically the same as even the top-speed contenders.
On top of the cost and performance balance, the M3 also comes with a 3.5-inch hard drive bay adapter to work with desktop computers and a generous five-year warranty. All this makes it actually a better buy than the M2 as well as many of its peers.
To find out more about how the drive stacked up against others, check out the full review of the Plextor M3 SSD.