Too much theoretical talking:-)))
You simply need a good SSD and the one in the post is!
You will not notice the differences people are talking about here. Just buy it! You will not regret.
I second this
Samsung is better in nearly all areas. People saying the Crucial is better are mistaken.
That being said, if the M4 is a bit cheaper or the 840 is out of stock, it's still a good deal. Fast and stable.
I'm not saying either is better. You can find benchmarks both ways. The only place you can find a difference in most SSD drives is in benchmarks though. Sure the numbers look like big differences, but only because they put them in milliseconds most of the time.
If you really want to get the most speed, only format 75% of the drive and let the last 25% remain unused. Or you can go with the 85/15 model. As the drive loses space to use, it needs to reallocate it more often. There are a lot of information articles about this, unfortunately I couldn't locate the benchmark one that proved this that I read last week. Most enterprise level drives come with 20-30% already allocated, which results in less performance loss over time and more wear leveling so they last longer, but at the expense of space being used - http://www.storagereview.com/inte...ise_review