Downtown Vancouver hotel rates are quite high these days if that matters to you. If you really don't need a car, a combination of transit and staying near the airport may be better. Some of the airport hotels are a no-change transit ride away from downtown and get a shuttle in the AM. Better than refuelling and having to deal with getting back to the rental location by 0430 or something for a 0600 flight.

If you are flying transborder, you want to be at immigration early - say 5 if not earlier - if you don't have Nexus. That's after checkin and baggage tagging (if I imagine there could still be some ski traffic that time of the day). Web checkin and filling in your customs car in advance will save you time.