IMHO - all three of the baler's you have mentioned are very good machines. One to add to the list is the CaseIH SB521 - which is the identical baler to the New Holland BC5050, but with CaseIH paint and decals. If there is a CaseIH dealer with a better price - good to know it is the same baler as the New Holland.
I just went through buying a late model, new to me baler and looked at all of the offerings thoroughly. My choice boiled down to a JD348 or a New Holland BC5070/5060 baler as they are 93 stroke machines. The New Holland BC5050 is 79 and the JD328 is a 80 stroke machine. 79-80 is really plenty. To put in prospective, our old New Holland 68 baler is 65 strokes per minute on a good day and it can keep a stacker hoppin' on a wagon.
Here are some thoughts:
Baler adjustment/running to get a brick shaped bale fussiness: MF 1835 easiest, JD328 next and NH BC5050 potentially the hardest. You can google and read all day long the above. NH can and will easily make bricks with the best, most newest baler's out there, but IMHO, they are less tolerant of out of adjustment, poor windrow management and baler feeding - just more fuss potential. However, if you have half a brain, banana bales won't be an issue. Even my old 68, once refreshed and tuned makes a brick bale, one after another. The MF/Hesston inline balers sound to me like they can't help but to make a perfect shaped bale ever time - regardless of the operator, windrow or condition of the machine. IMHO - JD balers are a close second. Beautiful bricks come out of our 348 - just in much more volume than the 68 and more flakes to the bale - which we want as we are selling to horse folks, hence for the 93 stroke machine. Had a NH BC5070/5060 came along with a good price, we'd have bought it. 93 strokes was the minimum criteria for OUR specific needs.
Parts and support - including internet help: Not even close. There is more parts and support for NH and JD baler's - period. Bust a needle or need shear pins on a NH or JD baler and are in a bind, there are generally multiple dealers within striking distance with your replacement parts. Deere especially shines in this department as I'm to understand they have a "machine down" program where if your dealer orders your part before 4pm, you have your part the next day. Internet support, again NH and JD just due to their massive number of sales over the years - someone has one of their balers and can offer advice - usually better than a dealer as most dealers have forgotten what a square baler is and don't have a clue how to service/trouble shoot one - especially the knitters. The JD 328 in many ways is very close in design to the 14T from back in the 50's, same for the NH BC5050. If you look at the chain driven flow action feeder in the parts manual and compare it to my old 68, they are strikingly similar. I'd give a slight advantage to JD as the 328 will be almost the same baler as the 336 mechanically and maybe the same if you exclude the wider pickup of the 328, which is wider then the BC5050. The 336 IMHO is a legendary baler, came out in the early 70's and tons of them were sold. Look at a 336 and 328 - very close to identical in design - which IMHO is important from a parts/support standpoint down the road.
HP: Any of the balers you have listed, 35 hp will run it. Though some argue with me, JD balers have a gear reduction on the input. This enables the baler to operate with a lower hp. I have 50 PTO hp to work with and I had folks essentially tell me considering a 93 stroke machine would be impossible.
John Deere 348 Square Baler - Baling 1st Cut Timothy Hay - YouTube
Wrong.
Other considerations: As I mentioned earlier, the pickup on the JD is wider than the NH or even the MF. I came within a hair of buying a MF1835, which is essentially the MF1836, less shielding. IMHO when they added the shielding, it made a simple baler much harder to service. This is why I didn't consider one when I bought my JD - and the MF1836 is a 93 stroke machine. Call me old, but I really enjoy an easy over the shoulder looks-see view of the hay feeding in the pickup on a JD or NH machine. If you are going to add options, like heavier drive line (some recommend this when using higher hp tractors) or a wagon hitch/extended bale chute, pickup gage wheel or multi-lumber for the knitters - do it when you buy vs the parts counter later. My 348 has an equal angle hitch. Pretty sure the 328 comes with it too. This allows for tight chatter free (from the PTO joints) turns. Drop dead simple. Resale - JD 328 IMHO has the advantage.
Recommendation: Any of the 3 balers you are looking at will do the trick nicely. If I'm choosing, I'd get the JD 328. Excellent machine, long long consistent production run, parts/internet support as good as it gets, wider pickup, your MF 230 will be at ease with it hp wise, even with a wagon behind the baler (careful on hills) and very tolerant to make beautiful brick shaped bales.
YMMV
Good luck,
Bill
Many around here just have the roof and are open all the way around, and they just hang tarps along the sides after filling. Very economical to build.