As someone who doesn't sharpen as often (or as well) as he should, perhaps I should stay below the parapet, but here goes.
The majority of my lathe tools are standard HSS, acquired second hand from multiple sources. They work just fine, didn't cost much and don't need sharpening unduly often.
I have two Crown PM tools which do seem to last a bit longer than HSS, but not significantly so, and I'm not convinced that the edge sharpness is any better than standard HSS. Only one is secondhand, as they're harder to find than HSS, so tend to be more spendy.
I also have a Crown M42 Cryogenic gouge and these do seem to sharpen better and hold a good edge for longer than HSS. Be prepared to pay, though.
Since HSS tools are perfectly adequate and available second hand, I wouldn't pay for the fancy metals unless I were a professional where (sharpening) time is money. Unless someone wanted to buy me a set for Christmas of course!
The only carbide tips I've used are the small round hollowing tips from Hope, which are very handy on occasion, due as much to the tool handle shapes as to the actual cutter.
I'm sure others will see things differently to me, but that's half the fun isn't it?
Duncan