We have rented from Hertz on the Swiss side a few times. No problems but I do prefer renting in Zürich as in Geneva you have to take a bus to the parking where the cars are. Last time the bus was full, had no air conditioning and it was almost 30 degrees outside. Fortunately my bags arrived late so KLM took them to the hotel.

We always rent automatic. Last time we got a small Mercedes, A200 I think. One thing to keep in mind is that you cannot drive the fancier Swiss cars into Italy, I think this is true for all rental companies not just Hertz.

In general it is cheaper if you pre-pay and also get the full insurance (if you want full insurance) online. I would say 700 CHF for a week is reasonable for a medium car including full insurance.