I got a used lathe last summer. We turned a lot of holiday gifts this year, mostly pens and other handles. I bought a set of full-size carbide turning tools at Rockler (square radius, round, and diamond). I also got the Sorby HSS (high speed steel) six piece turning set. I use a Grizzly sharpener with Tormek jigs to sharpen the Sorby tools.
I use both HSS and carbide tools when I turn pens. I start with a HSS roughing gouge, then the spindle gouge and skew chisel for shaping and smoothing. Near the end, I use the square radius carbide tool to clean up the final shape, and the round carbide tool to finish it and match it up to the bushings. At some point, I will be good enough with the spindle gouge and skew chisel that I can skip the carbide tools for everything but matching the ends to the bushings, where the round carbide scraper tool seems ideal for me.
In general, carbide is a quick way to get started with sharp tools, but carbide costs more over the long term. Replacement carbide tips add up over time. In addition, you may run into limitations of carbide once you achieve a high level of turning skill.
A decent HSS set costs more to get started, because you must also invest in a sharpening method at the same time. (Of course, you can use that new sharpener on your non-lathe tools, too.) In skilled hands, you can do more with HSS tools, and achieve a better finish on the product. That means less sanding at the end.
Carbide Turning Tools, based on my experience with the Rockler full size turning set:
* Carbide turning tools require less skill and practice to achieve acceptable results, but they ultimately limit what you can do, compared with HSS. It would take a lot of practice to reach the level of skill where it would make a difference.
* For the most part, carbide tools are limited to being used as scrapers. You can see by looking at the tools that the designers intended them to be used as scrapers. You can get bevel cuts from them, but that isn't the way they are normally used.
* Carbide turning tools are easy to "sharpen." Just rotate the carbide tip to expose a fresh, sharp edge. When the carbide tip is used up, replace the old one with a fresh, new, sharp carbide tip.
* Carbide is harder than HSS. It can never be made quite as sharp as HSS, but only experts would notice. Carbide stays sharp longer than HSS. It also stays "not scary sharp, but not really dull enough to rotate or replace" longer, too. Keep that in mind. :-(
* Carbide tips can be "re-sharpened" by flattening the back on a diamond stone. Flattening the back of your carbide tips may extend its life somewhat, but it won't be as good as buying a new sharp tip.
HSS Turning Tools, based on my experience with the Sorby 6 piece turning set:
* HSS turning tools require more practice and skill to use effectively, compared with carbide tools. You will make more mistakes and lose more wood learning to use them, but the acquired experience is worth the effort.
* HSS turning tools are more versatile than carbide tools. In skilled hands, you can do more with them. You can do exquisite bevel cuts on them, or use them as scrapers. Carbide tools have limitations compared with HSS tools, and are used almost exclusively in scraping mode.
* Sharp HSS turning tools are a joy to use. Nothing compares with the way that shavings peel off with a HSS turning tool. For me, turning with carbide tools isn't as much fun.
* HSS require sharpening. There was a huge difference in how my Sorby HSS turning tools worked before and after I sharpened them for the first time.
* HSS turning tools lose their edge more quickly than carbide, so they must be sharpened frequently to maintain an optimum sharp edge. It doesn't take long to resharpen them with a good sharpener and jigs, but some people are annoyed by it.
Rockler carbide tools that I have and use:
Robert Sorby turning set that I have and use:
Tormek Jigs. I bought the individual components separately, but this set would have been better:
I hope this helps.