About to apply for oyr first rental in Switzerland and looking at options for the rent guarantee rather than 3 months deposit. The agent suggested Swiss caution and First caution. Does anyone have any experience with the latter? Or Zurich.ch?

Be certain that the landlord / rental agency accepts the "Mietkautionsbürgschaft" you have chosen before you sign the contract for it.

These are the 2 most popular names in Switzerland, both are reputable. I have personally used SwissCaution before and have friends who use both companies.