Offshore? Hell, in Lake Ontario in five foot seas, I had a davit crack with a Zodiac 310 (10' 2") on the back. No engine.
After the Chinese fire drill wrapped up, I started my research. My conclusions? One 88 lb. nesting dinghy with oars/sail gear, and one 55 lb. 10 foot Portabote with 2 HP Honda (28 lbs.). Both on the foredeck.
My kid has his own "sailboat", and it's the "people mover" and the Portabote is for "cargo". I have versatility, capacity and a way to get separate trips done while at anchor.
What did I give up? The hassle of getting a 120 lb. RIB on deck that is a total wind scoop. The hassle of getting a 9.9 hp motor on and off its stern. The hassle of having the bloody pontoons ruin my forward view from the pilothouse.
RIBs are great for diving, hitting the softer sort of beach and going up windless rivers. But for our plans, they weren't ideal, and splitting one tender into two made sense.
Your mileage may vary.