Not done Zurich but Austria and Roth are similar enough course wise.

I've done Both Zurich and Austria. They were both fantastic

Swim: Zurich is better. Cleaner water (cleanest open water I've ever swum in) and you aren't funneled into a small area at the end as you are in Austria. In Austria the last few hundred yards are in a canal and good luck trying to pass anyone there.

Bike: Zurich is better. You have this long, 30k straight flat section that you go over twice. The climbs are a little tougher than in Austria but they are distinct and relatively short. In Austria it seemed like I was climbing a lot more often. The pavement in both is fantastic though

Run: Austria wins here. The problem with Zurich's run is that there are a number of times where you make 180 degree turns and such. Also the crowd kinda of stay a bit close when you run by the water and you can find it tough to pass people.

Overall I liked Zurich a little better. And when you're done... you're in Zurich which I prefer. I would do that.