I have a Telwin 150A gas/gasless MIG and it works well. I took it to welding class soon after I bought it and the tutor said they trialled them and thought they were quite good. Since they put theirs through a lot more than I could ever do (daily use by students etc) they bought Lincoln MIGs of about the same spec. My Telwin has 4 heat settings, the Lincoln they bought has 5. I'm not sure for home automotive use you'd stepless heat settings.

But with all these things, it's practice and thin sheet metal is by nature hard to weld. I would suggest that you buy a sheet of 0.8mm steel and practice with that. It will provide years of material for patching a mini, and is cheap (or at least good value for money). Who wants someone to look at your car and ask "Why does it say "Dell" on your front guard?"