The axle bearing issues with the 4430's were addressed, updated and rectified before the second year of production was rolling off the line. 4430's didn't have problems beyond the initial batch. Most that did have problems were covered under warranty. I know of TWO that were repaired on the owners dime.... 7 and 9 years after they were new..... A neighbor has a '75 4430 with over 12,000 hours, on a dairy farm no less, and hasn't ever had the rear end touched....And the ones that did need bearings and weren't covered under warranty were repaired for less than $2500 at the time. Last time I heard, it wasn't even $7000 in 2011 dollars to rebuild a 4430 rear end. Deere was ALWAYS better about rectifying warranty issues....A point where IH struggled miserably. (Remember the "tent cities" outside IH dealers when the rear ends on 560's started falling apart in mass numbers?) When the IH 1466's started shedding teeth in the final drives faster than new parts could be engineered and distributed, A good friend had his '74 1466 parked at his dealers shop for 16 months waiting on updated parts to show up.
Odd how your observations on 4440 vs 10 series IH and plows is the polar opposite as was the case here in our part of the country....4440's would flat smoke a 1066/1086, and the primary reason was the outdated, sluggish low flowing hydraulics and draft control IH stuck with until the ship sank. There were a ton of devout Binderoids around here that jumped ship when they got a sample of the butt whippin's their tractors took once the SoundGaurd tractors showed up.
In the end, all you have to do is look at sales figures from back in the day....Deere left IH in the dust. The 10 series IH's were "good tractors", sadly they ran up against a "GREAT tractor"......and couldn't ever catch up.
It's a moot point now though, as IH had to peddle their name at a fire sale because of pathetic management and sticking with outdated designs until there was nothing left but to hoist the white flag, and Deere has gone on to bigger and better things.....