Bowsers normal grab isn't that much faster than his dash grab, it comes out only one frame earlier. The dash grab also has 8 frames more lag, but I prefer it for its range, too. However, the lag of both grabs is ridiculously high compared to other characters grabs, of course.
@ Dikastis Shok:
Are you talking about the timed fortress hog? For me it's easier to slow the fortress down manually by rolling up the control stick a bit (about 45 ° or more, if you want to be careful) before reaching the ledge. The effect is the same, Bowser loses some momentum and grabs the ledge instead of flying past it, but you don't have to wait for the ending animation.
It's just like wavedashing to the ledge with Luigi, if Luigi is too fast when sliding off the ledge, he won't grab it.
Well, at least I believe it is like that.^^