A muzzle brake
will not affect the speed of the bullet.
Magna porting is one of the least effective means of recoil control. Look at the Brownells or E. Arthur Brown website to see the many different shapes and designs available for muzzle brakes
There are really two categories: expansion and baffle brakes. The expansion brakes are like the KDF, BOSS, and Weatherby style. An extension with a bore much larger then the bullet. This brake will have holes around the periphery of varying size and pattern. Work quite well, from 45 to 60% recoil reduction depending on port volume and cartridge.
The baffle brakes are like the fish gill brakes seen on 50cals, JP Ent, etc. Very effective, usually bigger in size and diameter. Effectiveness is a byproduct of number of gills and port/muzzle pressure. Usually better then expansion only muzzle brakes.
In either case, the more gas that can be diverted 90deg. to the bore, the better. The bigger the port volume the better. Lots of small holes or a few big holes really doesn't matter as long as the volume is the same.
Quiet brakes usually have lower recoil reduction then "noiser" brakes- allow more gas to be vented forward.
The most effective brake is the baffle brake that vents backwards - see most 50Cals. Also, the noisiest, highest muzzle blast.