CRUCIAL IS STEPPING out from Micron in the branding world, and is doing so by introducing a new drive. Welcome to the new Crucial M4 SSD, it is not the same as the Micron C400.
The physical drives are the same, 64-512GB SATA3 1.8 or 2.5″ SSDs. The newer C400 raises the read speed to 415MBps from the 355 of the C300, and the write speed goes from 215 to 260MBps. Basically, the C400 and M4 are second generation SATA3 drives, but the specs are identical. Where they are differentiated is in sales and support. The Micron C400 is an OEM drive, and gets sold in bulk packaging, and support is through the PC OEMs that resell them.
If you buy the Crucial M4 SSD, you get basically the same drive with direct support, likely a different software package, and accessories. The price difference is not going to be extreme, and the warranty support is probably worth the extra dollar or two.
This brand differentiation solves a really big problem of OEM parts. If you have ever read up on the spec sheets for a component, there is usually the same part listed at two or three different SKUs, sometimes with radically different prices. HDs are a commonly afflicted category, but the drive is usually the exact same thing.
The difference is in the bundle and the accessories. The OEM version typically comes with a shorter 1 year warranty, if that, and you feel lucky if you get a driver CD. The full package tends to have a 3 or 5 year warranty, comes with cables, dongles, software, and a comprehensive half page installation piece of paper with line drawings that look like instructions on how to ballroom dance in zero G with a ferret.
Whichever one you choose, you will get the same drive, probably the fastest one on the market right now. Whether the extras are worth the cost is up to you.S|A