I'm a well known snap-on snob but I I'll try to give you some objective advice
from a safety point of view, cutoff tools should always have a metal shield installed.. cheaper air tools may work ok for rough sanding n grinding but may not operate as smoothly for fine detail work with diamond cutters and burrs.. last thing you want while clearing out a tight corner, is have a wobbly tool throw a cutter out of the work area doing serious damage.. amount of work you expect out of the tools should also be a factor.. whatever you buy, make sure bearing glands are adjusted for smooth operation and keep them oiled.. better quality cutting tools typically make cleaner cuts.. if your not very experienced at sheet metal trimming, might want to try some test cuts on scraps to learn the angles and feed pressures the tools and bits like best
good luck!
I've used these blue-point and mac cutting n grinding tools for about 20 years at work and home with zero issues
