I'm not sure where you read that Intel x25 is not that fast. It's generally known as being among the top SSD's even if it's not as superior as it used to be, but still among the best. You cannot compare SLC and MLC though because SLC are normally faster and a lot more expensive and last longer as well.
It's often hard to say which one is the fastest because the Samsung could be faster for some operations and the kingston for others. Some might have very fast writing and others reading and so on. So if you pick a couple of the top SSD's available i'm sure you will see that benchmarks will show different results based on different kind of tests.
You could check out some benchmarks like this one to compare:
http://www.tomshardware.com/charts/ssd-charts-2010/Desktop-Performance-Index-50-Throughput-25-PCMark...
There are many kind of benchmarks to be found and you will find that some SSD are pretty high up on every list in almost every benchmark. From what i have read Kingston seems to be among the slowest while Samsung seems better. I don't think neither of these are the best you can get though, but based on these i would have picked the Samsung.
There are also a lot of info and reviews here:
http://www.anandtech.com/tag/storage
You might find review for both the Kingston and Samsung here that could help you out to pick the correct SSD. At the end of the day there is a lot of opinions and no correct answer, but some SSD's are simply faster than others of course.
Also they should work fine with your T510.
-gan
