I'm pretty old-school so.always recommend HSS for general use, the skills learned in grinding and tool geometry will serve you well as long as you're machining, and they are much easier to sharpen to a proper clean, razor sharp edge - this has a huge benefit in finish and tool forces.
The (usually Chinese or Indian) brazed-on carbide tooling is, frankly, crap - the tip geometry is wrong out of the box and needs regrinding on a green (silicon carbide) wheel and finishing with a diamond hone or wheel before use, so AVOID, the indexable inserts aren't much better!
Quality indexable tools from the likes of Sandvik are much much better, but understand that they're intended for heavier,more powerful, more rigid lathes taking heavier cuts in industry and don't work well on fine cuts on small lathes - the geometry isn't necessarily suited to hobby machines (negative rake on cutting edges, radii on them which force a minimum depth of cut). The inserts for aluminium have much finer edges and positive rake and can work well on steel on light lathes though, but decoding the part numbers is an hour's work when you could be working at the lathe...
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I appreciate that stainless is what you intend to work with but it has some awkward characteristics, worst of all its habit of work-hardening if the tool rubs rather than cutting, so if the cut (a couple.of thou" finishing to size, for instance) is smaller than. the carbide cutting-edge radius it'll just burnish and harden the Work... And decent (cobalt-alloy) HSS should cope with most stainless alloys and takes a much better edge.
If you don't feel up to grinding HSS tooling, there are sets available ready-ground to get you started and you can study their geometry and resharpen as you go along, gaining old-school skills
