So since RenBTC is not a real bridge and WBTC is centralized due to BitGo, the only safe way to do this would be to immediately sell the wBTC for ETH and hold that on the ETH chain? Or some other stablecoin?
It depends on your wishes you should have a reason before doing it.
Both are good in their own use cases, for example you want to gain access to ETH "defi" ecosystem or something like that. Converting BTC to ETH/stable coins just to hold doesnt have many prominent advantages.