Do these brakes have a closed bottom like the A2 to reduce dust signature?

How big of an issue is this?  

Some guys are always saying A2 so they can reduce the dust signature.  

Others are saying Phantom and Vortex so they can suppress flash the most.  

How big of a difference is their in the latter twos ability to suppress flash compared to the A2?  Is it enough to put up with thier inability to lower the dust signature?

i have the new 5c2 phantom which is the closed bottom one and i also have the a2.

alot of times i shoot on the bench and it does reduce dut kick up alot compared to when it was open muzzle.

i was able to shoot at low light the other day with both the a2 and the phantom and i feel that the phantom is a little better at reducing flash. with the phantom all i saw was a tiny fireball inside the fh and with the a2 i saw like a lil star coming out of the fh

but then again i doesnt matter cause it is so hard to tell doesnt really make a difference to me they both work