I've extensively used (among the higher end stuff which is worth bothering with) Hensoldt Spotter 60, Leupold Mk4, Optolyth (all of them), Vortex Razor and Kowa's in both Prominar and non-Prominar lines as well as darned near all of the lower end things from Celestron, Barksa, NcStar, Bushnell, and more. Kowa and Razors are the most popular on a lot of competition firing lines as far as decent quality goes. Others are there much in smaller numbers too.
Kowa in the non-Prominar line are about on par with Razors and with Optolyths optically. In the Prominar line, there's simply nobody as good as Kowa except maybe the 100mm Optolyths, and that's a fact. Kowa has what I think is a better color rendition. Razors feel really bright to my eye leading to some fatigue, like a lot more blue vs. red than might be ideal is being transmitted. Kowa gives a very natural color rendition and I can look through them all day long. Hensoldt and Leupold were not as pleasing to me visually but I don't have super specific complaints about them.
Hensoldt are fanstastically expensive and optically brilliant while being pretty light and compact. In a light/compact/reticle equipped spotter, nothing like the Spotter 60 from Hensoldt.
Leupy's are about the same as a Hensoldt to my eye but I didn't like the color on them, felt dark.
Optolyth are about as good as good gets in every way except price. The 100mm Opto's are the only thing I think even begins to compete with the Prominar line of Kowa's. Their smaller scopes are also simply brilliant. They're a bit more expensive than Kowa's.
Razors are also super expensive and wonderful to use. They're a little bright for me and I get a bit of fatigue using them for more than about 20-30 minutes at a stretch.
Kowa's are the choice of serious competitors in gobs of disciplines as well as being exceptionally popular with bird watchers (that's a diagnostic right there, birds watchers are nuts about their optics). I have and do stare through a kowa for literally hours on end pretty regularly without eye strain.
Honestly, among those I've listed you'll have a very hard time finding something you won't like except for the price tags. I've used them all a lot and I would be happy as a pig in poo with any of them. I own a Kowa and would like to add an Optolyth if that helps give context.
