Zeiss, Swarovksi (and their Kahles line), Leica, and Schmidt & Bender all make really nice stuff. My observations:
Zeiss stuff in most lines in the USA is "economy" and on par with Leupold and others. They make some really choice stuff but almost exclusively for EU consumption.
Leica is really overpriced for what you get. I buy a lot of it on closeout for 1/2 off at which point, its a great value.
Schmidt & Bender is quite durable, probably the most durable. It's also the most fussy when it comes to eye relief.
Swarovski is the best price/quality nexus of the bunch, and the Z6 1-6 EE and the Z8 1-8 EE are the most useful scopes I've ever owned.
At full boat retail, if you're not finding a steal/deal, go with the Swaro. If you're buying used and getting good value, all are fine optics. If you want a rail scope, there is a fine one for sale on the classified by S&B at a good price right now.
In vintage scopes, there are great models from all the above and from Hensoldt, Wetzler, Pecar, Docter, Habicht, and others that are a fine choice for the <$500 price tag. (1970s-1990s stuff that is just beautifully engineered and better than what you can buy new at that price)