How to judge quality of SDS drill bits?

[Ollie78]

Just bought a Dewalt Extreme from toolstation, very good indeed.
Has an end almost like a chisel tip but with a little point on the centre . It is easier to start than the more common V point ones I mostly have. Just drilled a bunch of 12mm holes in a concrete slab no problems and super quick.

 

[ukworkshipper]

On a slightly unrelated note, how long do the scews have to be in relation to the length of the rawplug? In the back of my Fischer box set it seems to suggest they have to be shorter but then online I have read that they have to be longer.