Yes there are a few differences...adjustable are more expensive and unless something is wrong with the adjustable it will stay at the pressure you set it at and you will know what that figure is. On a preset of any make you won't know and should something happen to yours and you borrow a teammates even of the same make and output rating odds are seriously against it being the same output as your "broken" one.
Any kind of pressure related tech work as having a set input required or reccomended to be used will be impossible with a preset as the LP versions are too high for most of these jobs and vary from reg to reg and the varience apllies the same for the HP versions.
The other thing I do not like about presets is the length they add to your setup (that of course is a personal thing not tech related
) also when removing a preset I would constantly be worried about the valve staying put and the bottle flying off..and this was way before the fatal accident with the CO2 bottle in the states. I will qualify this a bit as most all presets do not have any way of screwing them into the bottle by a sensible means to torque recommended figures..so adjustables only for me.