There is no doubt a mig is easier to use. Stick welding is stronger and I like that I can bend the tacks more when mocking something up. A stick will also weld out in the wind where a mig won't.
That being said I do 3/4 my welding with a 210 Millermatic. Using the stick when I'm out in the field.
Mig allow you to weld thin material and easily fill oversize gaps, which is just a way of saying I should spend more time fitting things perhaps, but in a repair shop it is usually a case of making the best of what you have to work with.
Mig is so much easier to strike the arc which makes tacking a breeze. Also nice to never run out of rod before you are ready to stop. Because the process runs cooler it tends to warp the material less as well
Stick will tolerate dirty material better then mig though
I generally keep it spooled with .035 wire and rarely run the heat over 4 out of 7.
I guess a 150 amp machine would cover most of what I use this machine for but I did not want to come up short on heat when I need it.
I would suggest getting at least a 150 amp machine. Those little 120 volt machines are not big enough to work with 3/8
I'm by no means a professional welder, I do repair welding and build god only know what next, I have learned as I go. While what I do may not be always technically correct, it gennerally stay together. I have never taken a welding course but i have built a few trailers and other bigger and countless small diy projects
I would try to stay with the major brands in hope they would support the machine with parts longer but that is something you never know until you need it.
I'm sure other will chime in
Skidsteer.ca
I used to have a 190 amp copper wound machine, it worked great, it still does in its new home too.
I now have a 250 amp machine, i love the extra 60 amps. I can weld 1/4" full thickness without an issue.
Ken already pointed out that stick welders have their place. Stick welders will work on rusty metal, have far better penetration. MIG really don't like rusty metals, if you give the weld surfaces a rub with a grinder first, it will be fine.
I assume you are going for a gas style setup? as in you need a bottle of shielding gas, the gasless style isn't as good and the finish is not as good either.
I'd lever give up my stick welder, i mostly use the MIG as its far cheaper than buying rods and no need to stop welds half way through and chip off slag.
I use .9mm wire, not sure what that is in imperial, but i can weld really thin metal with it if i turn the power down.