All depends what you want out of your machine, I have steppers on my Bridgeport and they work well, at the time I did that there was a BIG difference between servos and steppers because the cheap Chinese DC Servos were not readily available at that time.
It works well and has never given me problems but it is slow, 2500mm/min rapids (100IPM) and accel is not lighning fast either but as I said it works well and its fine if you are not in a real hurry.
Never tried DC servos with the likes of the Geckos so cant comment on them.
On the Lathe and Beaver Mill I use AC Servos and they are blazingly fast both in rapids and accel but you need decent sized ones to do that, you could probably use 0.75 to 1Kw with some gearing but for me 1:1 gives the full benefits of the AC Servos so I have 1.5Kw on the Beaver axis (bit bigger than a Bridgeport) and 7.5KW on the spindle, the lathe being a big machine needs 3KW on the axis and 12.5Kw on the spindle
AC Servos are not cheap but the drives give you many more options than the standard DC drives such as Geckos/Rutex etc.
All boils down to what you want out of your machine and how much you have to spend.
Hood