sharmab31 :
Want to replace hdd of HP2000-425NR with a SSD. Which of the above two models will be best suited?
There are plenty of benchmarks that will show you that for reads is the same performance, but for writing it will slower on lower capacity drive (like MX100 256 GB). MX100 512 GB will be the fastest between those two in general.
If you go for a RAID setup, make sure you understand what RAID is and what it isn't. RAID was designed for slower (and relatively cheap) hard drivers to work together either to gain faster access or to prevent failure of mechanical drive through mirroring, which would make it faster and easier to replace in a server environment.