If you are looking at laser as a comparison to plasma cutting....you should be looking at a high definition class plasma system as opposed to the air plasma that you are referring to! The Powermax45 is an air plasma that is designed to be a low cost, portable air cutting system. It prodces a wider kerf, slower cut speeds, and uses air as the plasma gas. Comparing laser to air plasma is like comparing a Porsche to a Prius.....they are designed for different needs!
If you looked at high definition plasma (which is still less expensive than a laser, but much more costly than an air plasma) such as Hypertherm's HPR130xd plasma system, you will see that is can use different gas mixtures in order to improve cut quality and metalurgy on different materials. For cutting stainless in the thickness ranges your suggest, the plasma would produce its best cut using F5 (5% hydrogen, 95% nitrogen) as the plasma gas and N2 (nitrogen) as the shield gas. The cutting would be done at low current (45 amps or less) and the kerf width would be as narrow as an air plasma but with much better edge metalurgy and squareness.
A laser would likely use a high pressure nitrogen process.....gas flows would be much higher than the plasma, but would produce a narrower kerf width.
Any of the processes will produce some spatter on the opposing wall of the pipe. Often the spatter in controlled with compressed air flow, a sacrificial back plate, or water flow through the pipe while cutting.
Just remember...there are air plasma cutting systems and there are high definition plasma systems....when comparing to laser it should be high definition!
Here is a link to info on the Hypertherm web site regarding the HPR130xd plasma system.
HPR130XD - HyPerformance Plasma System | Hypertherm
Best regards, Jim Colt