Carport, hands down. I would guess that very few people actually cover their RV every single time they are home, immediately after getting home. Get home late or in inclement weather, don't want to deal with it. Going back out in 2 weeks, don't want to deal with it. Cover put away wet before the weekend trip and still wet, don't want to deal with it. Its windy when you get home, don't want to deal with it.
Carport... back under it.
Its more expensive at first, but it a cover costs $300 and lasts 3 years, they quickly get expensive. My $2400 carport (18' wide, 31' long, 10' legs) will last WAY longer and be WAY more effective as it covers it all the time. Mine is wide enough to leave the slide open and provide easy and dry access to load or unload, no matter the weather. It keeps the snow load off the roof (had almost 3' of snow earlier this year... that's a lot of weight on the roof!).
My father in law had a cover for his camper and was VERY diligent about covering it, storing the cover when not in use, drying it out, etc. He just bought a new camper and is getting a carport. Too much work covering and uncovering.