Hey Piston,
I sold my TT75A (great tractor) and had narrowed my new one down to a T4.75 or a
M7040. I almost pulled the trigger on the orange several times because I was having a heck of a time finding a T4. Barlow's had several
M7040's and he priced them right. Plus the Kubota had a better warranty, 0% for 60 (vs 0% for 48) and was cheaper. However, I kept thinking about how nice the cab was on the NH and how nice it was laid out.
I finally got a T4 specd' out the way I wanted it and have been very happy with it. As foreman mentioned, the tractors are the same size. The Kubota is a hair taller and the Kubota has 9.5-24's on the front where the NH has 11-24's.
Concerning the 540E, I pull my Bush Hog Squealer SQ840 (7' rotary cutter) on the 540E setting and it runs out just fine. I didn't get around to my first cutting until July so the stuff was thick. It rocked on with no problems. Your throttle is also "governed" in this setting, you can't push it past somewhere around 1700 rpm or so. Used a Land Pride 15' batwing (RCRM3515) to take care of the bigger fields but use it in the regular 540 mode.
The chart I had posted from Kubota showing the comparisons was a bit inaccurate. Some of the T4 and C75 info was premature or simply unavailable. The Case should have shown a wet clutch was available with the shuttle shift.
Dirtiest pic so far :
And I do realize it's not even that dirty.

I was bushhogging behind the dam of an old pond that has a decent leak. She sunk down pretty good (especially with 4,000lbs of dead weight - batwing), but with the flick of a switch, she backed out just fine.
jdbnh, ljohnson778 and foreman eTexas were all very big help to me during my tractor research / purchase phase. I certainly appreciate all of their help as they are a great source of info.