it will shoot as fast as your fingers can when set in semi auto mode, i personally find the triggers on them nice and easy to 'walk'
as to will it shoot faster than a proto rail, in semi i would guess a rail will shoot just as fast, all down to set up and personal taste.
only way to truly tell if one marker has the ability to shoot faster than another is to put the same hopper on both and put them in uncapped full auto.......in real life the numbers are very different and unlikely to vary much from one gun to another, how fast your fingers are is the main limit and then once you hit a certain point how fast your hopper can feed.