MIG welding is definitely the easiest to master and can be used on steel tubes and plates. I've had absolute beginners producing good welds with just a few minutes tuition.
However the welder you're looking at isn't a real MIG it's one of these,
Flux Cored, just a glorified stick welder and at 150 amps it'd not blow your socks off. Personally I'd give it a miss, pay a bit more and get a proper welder! You can run a 250 amp machine from a single phase 13amp socket.
Arc/stick welding is rough and ready but can produce good welds with practice but the big problem is removing the flux afterwards. More for construction, blacksmiths and emergency repairs in my opinion.
TIG is expensive, very difficult to master, slower but far superior to either of the above and you can weld a wide range of metals with the right filler rods.