More heat, not necissarily "hotter" (think of 1 match vs 2 matches).
MIG welding being a constant voltage process, leaves the amperage dependant on the feed rate or deposition rate (wire speed). Cranking the wire speed requires the amperage (and therefore wattage) to increase since the machine is maintaining a constant voltage.
In my experience, small hobby/light mfg welders such as these run .030" ER70s-6 as the "standard" solid wire.
If you need more penetration for thicker structural type welding, then you do not want to use a solid wire like ER70s-6, especially using a small machine. Gasless flux cored wires are just messy, so I don't care for those. What I recommend you try is a dual shield wire (gas and flux cored) such as Lincoln Outershield 71M or ESAB 7100 Ultra. I have literally hundreds of hours under the arc on these wires and it is an awesome wire to work with on materials thicker than 3/16" or 1/4". If you're already running shielding gas, then get yourself a 10 pound roll of .045" 71M, the required knurled drive rolls for non-solid wires, and the larger liner for .045" wires, and give it a try. Your welder will burn into thick material like a stick welder and make beautiful welds and you'll be able to quickly change between thin and structual jobs.
