I don't think it's quite as dismal as samsung or get sub hdd speeds. In some performance tests the mx100 outperforms the same sized 840 evo. The 840 evo does perform a little better overall, but is usually pricier. The evo is currently going for around $10 more than the mx100 which makes it a better value. It just depends on when the sales are. When I caught the ocz vector 150 240gb for $60 on sale I grabbed it. The evo does have 62% faster random read than the vector, but the vector is pretty much faster at everything else by 30-60% netting it better performance than the samsung in both real user bench's and lab bench's. The only place samsung fared better was value since it's usually cheaper, but it was half of what a samsung runs when I grabbed it so it beat samsung out there too. Not saying samsung's are bad, that would be a dumb thing to say. They aren't the end all be all of ssd's though. Ocz makes some nice drives since toshiba picked them up, intel ssd's like the 730 series are also strong performers.
It comes down to choosing between the best of what's in your budget and taking advantage of specials. Going back to the original question between just the drives the op mentioned, given current pricing the evo is the better choice.