I just see a lot of work, and skinny cattle rummaging around.
But, if I HAD to pick...The IH 990 looks like it is the closest to making hay. The battens on the reel are all still nice and straight. It's old and rusty, but probably hasn't cut that much hay.
Until some Amish/Mennonite workshop rescues us, and starts making conditioning rolls for old NH haybines... there will be quite a few, otherwise serviceable, units being cut up for scrap, for lack of conditioning rolls. They are unrepairable, and a fatal flaw, once they go bad. That old 477 is a cryin' shame.
The New Holland parts situation is dynamic and changing every day. We run two old Hesston 1070 haybines that we got for scrap price. When I got them, 10 years back, they were considered mongrels and old NH haybines were respectable...
But... at this point, the probability of getting parts for IH, NH and even Hesston has come to even odds.
Going into the future, it may even lean towards our Hesstons, as they are made from standard parts (bearings, gearboxes and such), no wobble drive, with steel rollers that never delaminate.
One defense mechanism I have, though... is I need to keep a healthy stock of guards and sections on hand, as they are harder to get than NH.
If you ever consider a Hesston... the one common weakness that I've noticed is the reel drive. We keep a 10' length of #40 roller chain and a master link in the shop at all times...
I'm not sure what the guard and section situation is for an IH haybine.
Overall, you asked "which one," and I answered... but we're currently running haybines with an eye toward scrapping them in a few years, not buying in to the technology... again, unless some Amish/Mennonite shop changes that situation.
The main thing that holds me back from going to disc mowers is... there is no seven foot disc mower/conditioner. I would have to jump up to nine feet... which doesn't work well in the small fields and gates that we go through... and would require larger tractors than we run.