LittleBee 20A ESC and DYS BL20A ESC, does it matter which one I use? 
They seem to be similar in price and size, any difference between them?

It matters a lot! LittleBees are much newer than DYS BL20A.
Go for LittleBees, they are far better ESC's and have stronger braking, also flashable via CF passthrough.

How about comparing them to Kiss one ?

Kiss ESC's have better performance than little bees, but they cost more and are likely to catch fire. Little bees are a safer option and still great performance
LB are actually very close to the performance of the KISS ESC's but at almost half the price.

If you use littlebees then you must have lc filters on your rig. My qav210 cant be flown properly because my matek pdb sucks!

Also the Little Bees have a slower F330 processor that may struggle with high eRPMs and may have trouble with Multishot. In terms of future proofing, F39x based ESCs would be better.

But Its not an issue unless your running high kv motors like 3500 and up and 4S batteries. Then yes a F39x ESC like a Angry Beast would be needed.

Is Angry Beast the only ESC using F39x based chips?
How about the newer DYS XM20A?

It might be only me, but I feel little bees are more powerful than dys20. I have both on similar setups.