dragging stuff out of a pickup truck = deck over = seating-> rolling -> getting up / finding step stool to get up on it
dragging stuff out at knee height = regular trailer = nice easy hiking leg up and walking up onto deck.
i guess it goes a tad further, deck over the wheels, deck between the wheels, along with axle under or below the leaf springs.
the trailer i have = deck between wheels, with axle seating above the leaf springs.
for myself i am not hauling cars, or tractors all over the place. i am hauling everything else, lumber, firewood, dirt, rock, crud to salvage yard, or local waste places, and its nice having that step up on ability.
i have 2x4 sides i have for it. (takes 2 folks to place them on and tie them down) but helps being able not having to lift sides so high.
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heavier stuff as in actually hauling tractors, skid steers, cars, trucks.... a deck over would more likely be beneficial. due to wider deck, and not having to deal with wheel wells, ya deck may set higher but...so much more room to work with. and ability to load/unload pallets of what ever easier (assuming you have fork lift or tractor with FEL forks). and more so ability to place pallets were you have correct tongue weight.
higher the deck height from ground = longer ramps, and dealing with longer ramps in either how they fold up, or slide up and under the deck can be a bigger issue, along with some sort of legs or something on rear of trailer, that keeps the rear of trailer from going down. so when ya go to load something heavy (car/truck/tractor) ya don't pick up rear of truck, and having it all take off on you down the hill. ((it is that initial driving up on ramps part that can get rather ugly)) without some sort of rear supports you can put down. sometimes built into the ramps, other times you need to physically drop something down and tighten it up. or even block up rear of trailer with some lumber.
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i am not a large fan of tilt bed decks. they have there uses, but not for me.