Only issue with 5x4 is hauling them, makes you 10 feet wide on the road.
Yepper, if you are a long distance road hauler; most folks aren't. That is one of the main reasons the 5x6s with a foot chopped off (4x6), the other reason being that they are becoming the norm and can be sold for what the larger bale brought with 20% less product. Personally I like being able to see around the bale when hauling 2 (one FEL the other 3 pt) which was a problem even on my 100 horse JD 4230.
Edit: ".........The rest of the story" (Paul Harvey):
When I retired I downsized from the 4230 to the 6530. I sold my 5x6 roller which could put out a 1600# bale under pristine conditions, for one putting out about half that which I could better handle with smaller equipment, both in rolling and in hauling.
Not knowing better, I was looking for a 4x6 which I saw others using in my area. None to be found. What I did find was the 5x4. Do the math and the volume of the two are about the same; close enough.
The 4x6 benefits were:
-As previously stated, 2 side by side were within DOT width requirements for OTR hauling.
-course any of them can be adjusted down to 4x5 or 4x5.5 if you are selling by the bale.............which is what happens around here...no scales handy.
-With the mouth at 4', your pickup area was within the spacing of the tractor's tires for something big enough to pull the baler.
-With the narrower mouth, a good fluffy windrow would fill the mouth and you had good bale fill and a good square fill....no barrel bales like would happen with a 5' mouth and a narrow WW or no weaving back and forth. You don't have to weave with a 4 footer.
-commercial operators are more apt to use that over the 5x4 meaning that any found for sale were probably well used. I can compare that to my 4230 at 100 hp, no turbo. The turbo version 4430 put out 25 more hp. It was popular with farmers around here as it was a work horse. Finding one, 10k hours was the norm and the offering price didn't discount the high hours. I bought the 4230 sitting side by side with a similarly restored 4430 for $2k less ($17k vs $19k and a much tigher machine) and 3900 original hours vs 10k. I figure you can expect the same with the baler.
Hope that helps you in your pursuit.
Mark