The swarovski isn't worth that much more cash. The Zeiss is a great scope more than enough than is needed to shoot well and the glass is excellent.Zeiss has been making scopes for a long long time they know what they are doing. If you want to pay more you aren't going to get anything that will actually do better. There's a point of diminishing returns.
I guess that's why both are in business. To my eyes the Swarovski outperforms the Zeiss. Not saying by much but it is there. Where Swarovski pulled ahead by miles is in the reticle department. Swarovski made the TDS reticles which I liked (have 4 of them) and they are making the Ballistic turret system which I find very useful on some of my rifles, (3 in fact). Zeiss has the rapid z system which is way too busy and confusing to ME. Others love it and that's great if it works well for them. In low light it is so busy it looks like you're shooting through another tree.
Swarovski's rail system is #1 in that the scope is locked in place with the teeth from the base and the teeth under the scope. Zeiss's system isn't quite a strong. It is however better than Schmidt & Bender's system which relies on simply having enough torque on the pieces to keep them from moving.
Also from what I've experienced in dealing with their offices here Swarovski has come out ahead. I bought a 6-24 PH a couple years back that had been on a rifle that was knocked over at the range and the top target turret was broken off. Definitely NOT a warranty issue. I called them and they said to send it in and it would have to be returned to Austria for repair. I had no idea what it was going to cost and they couldn't give an estimate because they didn't know what else might be damaged in the controls. Made sense too from their point of view. I shipped it to them and waited for an estimate. Month and a half later I hadn't heard anything and called SONA and asked if they'd ever gotten an estimate for the repairs. She said no and stated that they had just gotten a bunch back that they'd sent in for repairs. She came back shortly and said it was in the batch and the charges were ZERO. They paid the insured shipping back on top of fixing it for free. They had not only replaced the broken turret but updated and replaced the other one since they had new style turrets out by then. No charge for anything and all cleaned up and like new.
Earlier this year I bought a Z6i 2-12x50 TDS-4 from a woman in Florida whose husband had passed on. Paid $1900 for it and when it came in the illumination module wasn't working right on the low side. Again sent it in and they shipped it to Austria and replaced the entire module with a new one and sent it back. My cost was sending it in. No hassles, no arguments, just outstanding service.
Little over a year ago I called Zeiss on a Silver 4.5-14x50 that I had. At the time I hadn't had a Rapid Z and from the pics thought that would be similar to the TDS. I asked if they could swap the reticle and how much it would be and was told to go buy a new one. They didn't have time for stuff like that. Well I did buy a new one and sold it a few weeks later when I found it was not what it appeared to be. Recently traded the gun that had the Zeiss on it to another fella. There was nothing wrong with the 4.5-14x50 and I really did like the clarity of the scope. However in my world it comes down to the reticle and I don't care much for plain reticles anymore. IMO Zeiss is behind in the reticle department. For those who like what they offer that is fine and I have no problem with that. But they don't' fit me so Swarovski is the only option out there as far as I'm concerned.
Also in the weight department Swarovski is killing the competition. I had a Z5 3.5-18x44 earlier this year that was super light. 15.9 ounces for a scope that size is unheard of. If you are aiming for a light weight rig the Swarovski will give you that setup.
Granted in the low end Swarovski and Zeiss scopes the Swarovski's do cost considerably more. Zeiss is kicking butt on that end of things. And I'm happy for them. Comparing their scopes to Leupold there is NO comparison. And the price difference is well worth going with the Zeiss. However when you go to the 30 mm tubes the cost difference is not nearly as pronounced.
As far as diminishing returns. I don't see it as a diminishing return considering the value of the scope doesn't go away like it would on a car or other 'equipment'. Take care of the scope and it will do well in holding its value. I sold my Z5 this past year for what I bought it for last year. Thus it cost me nothing to go first class. I traded off the Conquest and since I'd bought it right a couple years back I might have broke even on it but compared to the new prices it would have been $200 less than a new one, minimum that is.
Each his own but to be fair to the newbie they need to know all the ins and outs of what each brand has to offer. Then they can decide which fits their needs and their pocketbooks.