We went through this same exercise last year and ended up purchasing a slide-in Grandby. However, in a perfect world with unlimited resources we probably would have gone with the Flatbed.
The Flatbed floorplan is definitely more open and there is significantly more interior storage in addition to whatever exterior storage you build into the flatbed itself. So if you plan to do long trips or have more than a couple people along, then the flatbed will definitely be much more comfortable.
However, to install a flatbed you will have to have the bed removed from your pickup and have a flatbed installed. This is an added expense (potentially significant depending on which flatbed and options you choose) and probably will make the truck more difficult to sell if you ever want to sell it separate from the camper. My sense is that slide-ins are easier to sell both becuase they are lower cost, and because they don't require the same level of modification of the truck that the flatbed does.
Although it is possible to remove the camper from the flatbed, it is somehwat more difficult, and you are left with a flatbed pickup instead of a standard pickup. So, if you want to use your pickup regularly for hauling, etc., the slide-in is more practical.
This was our first RV/camper of any kind (we come from a backpacking/tent camping background), which defintiely influenced our thinking. We decided that the slide-in would be the most practical for us at this point in time. It is lower cost, and if we decide that the RV/camper "thing" isn't right for us, it would be much easier to sell the truck and the camper than if we have a flatbed. However, if we get the kind of use out of slide-in that I am hoping over the next few years, we still might decide "upgrade" to the flatbed (we bought our truck with this option in mind).
Of course your friend's flatbed is available now, so theres that...
Good luck with your decision making - I think you will be very happy with whichever route you decide to go.
Edited by heinphoto, 12 November 2020 - 06:08 PM.