I've got the mx100 256gb version myself, and an external 500gb. I don't really use much space though so I never fill my ssd more than 60% percent.
The mx100 has an excellent price ratio at 40c/gig. The samsung is a little more expensive but boasts a guaranteed lifetime.

SSD increase their write speed as they get larger, so ideally the mx100 512gb version is the best price/performance but it's still a large amount of money. The most worrying aspect of this ssd is the new 16nm process and how it pans out. From what I know the controller in it is a sturdy chip known for reliability.

I'm checking the PC component world almost every day because my 4870 x2 sapphire might be up for an update soon. The fact is plays skyrim on high is boss but it makes a lot of noise and the power usage is immense.