These are all high performing options. In the real world you won't see much difference unless you are stopwatching it with a benchmarking program.
Here are enough numbers to drive you batty. I've been running 3 M4s for over a year without a single hiccup. Personally I feel comfortable with their reliability.
When you are measuring access times in fractions of a ms, there is not a human on earth that can tell the difference.
These are read access times, meaning time from requesting a file from disk to start reading the file.
Samsung Serie 830 256GB 2.5" CXM03B1Q 0.10 ms
Crucial m4 256GB 2.5" 0009 0.04 ms
Intel 520 Series 240GB 2.5" 400i 0.08 ms
Samsung Serie 840 250GB 2.5" DXT06B0Q 0.03 ms
Compared to an economy drive like the western digital green @ 2.51 ms
You also have to remember when looking at benchmarks that the larger a SSD gets, the faster it typically is. A 500GB SSD is usually much faster than a 64GB SSD because it is able to spread the workload around between more chips.