issue 1 for me, keeping the stuff out of the weeds.
issue 2 for me, keeping the stuff out of the mud.
issue 3 for me, i will most likely use multi 3pt hitch stuff in one go, say bottom plow, disc, drag harrow, rear blade, all in one day. and not have a chance to go at project for another few days because of rain.
issue 4 for me, trying to turn tractor just right inside of a shed to drop off / pickup another attachment, "dirty attachment from just using it"
issue 5 not enough time before next rain comes along to clean between using different implements so they may stay dirty for some time.
issue 6 i hate tarps, a good wind, and a tarp will get destroyed quickly. from a sharp corner on the implement/attachement, to just trying to strap a tarp down to keep it from blowing off. not to mention mice and other critters wanting to build nests, if you tarp it up to good.
most 3pt hitch implements are built heavy duty enough to last years setting outside. the bigger issues setting outside, are the sun rays, on rubber (from tires, to hyd hoses, belts), and then rain/snow/ice, and the rust that comes along with everything.
=================
personally prefer a "lean to" shed, or extension to side of the shed, were roof just extends out say 6 to 10 feet from the side of the shed. just enough to cover stuff below, and keep majority if not all of all sunlight and rain/snow/ice off the stuff. i say majorty due to high winds coming around and wiping some rain/snow/ice up on to some stuff.
easily backup to each implement without extra stuff in the way, and i can turn garden hose on/ pressure sprayer on, without fear of getting everything else inside a shed for example dirty/wet.
not really loosing valuable floor space inside the shed itself. or wall space.
the bigger issue with this is, you need more driveway, to get around to side of shed, or you will be dealing with a rutted muddy mess if driving over lawn to get to the area.