PhotosBySteve wrote:
I own the Sony R7II a full frame mirrorless, as well as a Canon 6D & 7D. The mirrorless does NOT save anything in weight. The weight is all in the lens of choice, not so much in the camera body. If you want to reduce weight, replace the camera body with a small mirrorless or bridge camera, and any lenses with small, slow lenses. This will also reduce image quality and printable size.
Obviously depends on one's outlook on what "printable" quality size and structure means to a person. Having personally printed from 4" x 5" and 8" x 10" (in a Pro lab/studio I worked at) negatives before, I am astounded at the 30" x 40" print capabilities of modern MFT (my Olympus) and DX sensor cameras (my Nikons) having had printed those sizes in the past year from both. Snappy and Sharp on print, they are.
FF really, in my opinion, would come in play for me in lower light situations as in my previous 35 year stretch as a Pro Wedding photographer. The advantage of true F stop on full frame would be of no consequence either for me. At F1.4 on my 4/3 lenses, I have no problem with the slight difference of true aperture.
As to the OP's question of saving weight/space but keeping Image Quality - there is (in my humble opinion) no doubt! My Olympus kit is easily 1/2 the size of my Nikon DX bag.