i have a tandem for the old allis chalmers CA tractor. and right in the middle i end up getting a line that does not get hit.
if anything separates anything, it would be the stinking "adjustment" for how much angle you want. that you should pay attention to. seen way to many large size bolt / screw adjustments get totally bent to point you can not adjust anymore, and/or become rusted up that screw/bolt like action for adjustment becomes nearly impossibly. and then there are ones with bolts/pins were there is no bushing inside the holes. so you end up wobbling out the holes and/or bending bolts that you need to cut out due to bent to much to pull out. U bolts / muffler clamp like bolts. will want to slide out of adjustment. give me something with pre-drilled holes, and bolt with bushings in the holes. so what ever angle i want i can set it to. within a few degrees of angle. (how ever the holes end up and spaced nicely on the frame)
some folks want the discs nice and straight and parallel with tires, other folks want the discs and a much steeper angle. (depends on usage/wants)
some folks want extra weight to get everything to sink down into the dirt.
some just take factory set welded angle and deal with the disc how ever it is setup.
cleaners (mini shovel per say located on top side of disc) can be rather nice to remove clumps that can stick to the discs.
larger the disc is, more likely it will have hydraulic gauge wheels/transport tires to raise/lower unit. due to 3pt hitch and weight on rear end up end up with front tractor tires off the ground when trying to lift it out of the ground.
type of discs from full circle, to more of cut out / teeth of the discs can also matter in what you are wanting todo /use it for.
if you ever need to replace any sort of bearings, and/or pending on how things are greased at bearings. this can matter a lot. some times you got grease zerks or less non or broken off, other times you drop entire rod and discs and all, and pull everything off... can be easier or a nightmare pending on size/setup.
if you are dealing with forest / trails in woods, to rocks in the soil. to not field but off field usage were their is uneven terrain. i have hung disc up before on roots and rock, causing rest of disc to "hang up per say" as one side raised up and over.