Here is my thoughts… I have a 1533 with a 72” mower and it has no problem cutting my pasture grass here in Florida at low range 4th gear (high range, 1st gear tops). I have done some brush cutting with it and no problem there as well. I to wanted the bigger mower because of my fencing, but guess what? Get the “I need a 72” mower to get close to my fence”, out of the reasons to get a 72” mower, it still will NOT cut next to your fence, trust me on that. The mower is only about 5” wider (I think even less) on both sides of the tractor, it seems to be allot to get up to a fence rail, but it isn’t, you still can’t get up to the fence… In any case, go for the bigger mower for the reason of making less passes and not for getting next to something. It has been side here all over the place, you can make a bigger mower smaller, but you can’t make a small mower bigger.
72" weight... Not a problem. I have cut grass without the loader and no problems. Yes, I have had the mower all the way up on the 3point with no front end lift.
Last thought on the mower… If the 1533 that we are talking about is a hydro, forget about the 72” mower and go with the 60’, the hydro doesn’t have the HP to turn a 72” IMO.
About the 1433v and 1533 width… I am not sure what one is wider or not, but the 1533 comes with the adjustable wheels (remove from hub and make them wider)… Isn’t the 1433v wheels a solid wheel? If that is the case I think the rear track would be wider on the 1533 then the 1433v right from the start because of the wheels the 1533 comes with.
EDIT... Forgot to say I have the R-4s... Also here is the best pics I have right now with the mower on, again it looks as if you can get next to fenceing, I still have to use my riding mower. Remember the blade sits back a bit from the side of the mower.
(note the grass the tractor is sitting on in this pic is done by a riding mower not the brush cutter)