Ok, so lets compare the three models you listed.
None have live PTO. That pushing the tractor with a brush hog
deal applies to all of them. It can be stopped with a $50 ORC.
That's an Over Riding Clutch which acts like a ratchet.
When the tractor powers the brush hog, it turns. When the
mower tries to drive the tractor, it ratchets. Example
They can be purchased to fit different PTO shaft sizes too, so
that is something you will want to pay attention to before ordering.
They do not provide "Live PTO", that's another topic. :)
The 8N is a flat head Ford engine with proven longevity and simplicity.
There's nothing wrong with them at all. If you need to do the
valves on one, they are in the block, not the head, so you may
have to take the whole block into the machine shop if you can't
fix it yourself or don't have a travelling machinist. I still have one.
Keep in mind there were early and late 8N models.
The earlier ones had a front mount distributor similar to the
flat head Ford V8's. Some people get confused by them and
find them hard to work on. They're not to me, but they are different.
The later model 8N's had a side mount distributor and a round
can coil. Very much like every car/truck/van in 60's.
They are better understood by many local mechanics.
Both models about 23~25 HP and both models added position
control to the hydraulics that the original Ferguson system used
on the Ford 9N/2N did not have. So, make sure when someone
is selling you an "8N" that it's actually and 8N, not a 9N/2N.
I own two Fergies, but I'm not as familiar with them as I am
the Fords. However, they have proved their mettle too.
Valve in head design, tilt up hood, gas tank not attached to
said hood like it is on the N's.
Parts are not as readily available and are more expensive.
Some of the engines had a tendency to crack the block leaking
antifreeze into the oil, which, if not caught in time, detroyed
the engine. Not an issue normally if you're taking care of your
tractor, but definitely something to look for when buying.
Here again, models often get confused. Is it a TO20/TO30/TE20?
Be sure of what you are buying. The TO30 had a Continental
gas engine and was rated at about 28 HP. (numbers rounded)
Still the Ferguson system, so no position control.
The NAA/Jubilee model Fords were a valve in head design also.
Called a "Red Tiger" engine by Ford enthusiasts.
This was much the same type of engine that was in the Fergy,
but parts are far cheaper and easier to find in my experience.
Tractor was rated at about 30 HP, so not much difference there.
The big difference with this tractor is live hydraulics.
On any of the other options, the clutch has to be engaged for
the hydraulic pump to run and the 3 PT hitch to work.
If you want to set still and raise the lift, you have to put the
transmission in neutral, release the clutch, move the lift, then
depress the clutch and put it back in gear to move instead of
simply raising the lever while the clutch was depressed
And if you're lucky, the lift stays up while you put it back in gear.
Travelling down the road with a mower may require a blocking
system or that the PTO shaft be disconnected so that the PTO
can be left running to hold the 3 PT hitch up for the drive.
The NAA/Jubilee and up pump works any time the engine is running.
Issues with this tractor were that the rear end was not as
robust as it should have been and the external hydraulic lines
could be damaged. These were both addressed on the 600 and
up model Fords.
The Ferguson TO35 Deluxe also has these features and could
have had power steering. Which your wife might also appreciate.
The older I get, the more I appreciate my tractors that have it! :)