The M550 is the technically better drive. Sequential speeds are identical to the MX100 but the M550 is a little better at high queue depth 4k random read/write. Worth $25 better? I personally don't think so. It is highly unlikely you would be able to tell the difference. Save the $25 and buy a few humble bundles.
Bought the MX100 512gb, installed it no problem with windows 7, definitely working out and obviously much much faster
The MX100 is no doubt a quality drive, but apparently you need the 512 GB model to get the full speed due to the parallelism, RAM, and controller used. Probably wouldn't notice the slower speeds of the 256 GB etc models in real life.
