HST = speed up in areas were grass is not that tall / thick. and then slowing down just a bit in thicker / taller areas of grass.
HST = adjusting speed on the fly and no relient on gear you are in.
HST = easier to 1/2" your way up ti side of a pickup truck to load something into it. unlike a manual, that has clutch, brakes, etc... that might be on same foot. plus dealing with FEL (Front end loader) adjustment.
HST = you loose a couple HP over a manual/gear. but you will never feel it. you would have to be using tractor as a "day job" type of thing using it constantly to even notice difference.
HST = do normally have a 1,2 and hopefully 3rd adjustment gear. to pick a better speed range. hi/lo really does not cut it for some things, having a low / med / hi like adjustment more likely more beneficial overall.
HST = more power when barely pushing the pedal down. as you speed up (pushing pedal down) you loose power for RPMs / faster MPH.
one way to over heat per say a HST. is "pedal to the medal" in to high of a gear. most HST has internal max pressure valves. and they will kick in for example pulling to much of a load behind you, in to high of a gear. this can cause a lot of heat build up. lowering down the shifter (low / med / hi) will help keep the internal max pressure valve/s from kicking in. and keep you going smoothly.
other words unlike a manual / gear transmission when you overload vehicle or tractor, you might stale the engine out. for HST hopefuly the internal max pressure valve kicks in. (saftey feature for engine in a sense)
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"power reverse" for HST can be a big deal for many folks. ad's might state same speed forward or backward. many companies / folks use tractors for "loader work" a lot of say diging up manure, dirt, rock, etc... and dumping the FEL bucket into a truck bed, trailer or like.
without power reverser option. reverse can be rather slow.
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while a lot of work has been down to "manual / gear" transmission to reduce need to constantly clutch every time you goto shift to another gear, brake, etc...
i find myself in many situations, were i have "one foot" on the forward/back pedal. and the other foot on one of the "split rear brake pedals" and i no long have a foot to operate a clutch pedal, to get myself unstuck. and most likely one hand is on steering wheel, while other hand is on FEL (front end loader) joystick or 3pt hitch levers. to help get myself unstuck or just simply general operation of tractor.
for a multi purpose machine HST way to go.
now farmers on other hands. they might go 2WD, were they might get out on the road, and just upshift into gear. and they are done, or get into a field and set a gear and they are done on a manual / gear transmission.
to state things different "down town traffic" at nearest largest city near you. and hitting non stop "RED" lights. with bumper to bumper traffic. in a manual / gear transmission vehicle STINKS. and even worse when you are facing upward on a steeper hill going through lights. this is going to be you many times with tractor, operating FEL, or perhaps with something on 3pt hitch backing up, or simply turning around at end of driveway and around garage and like clearing snow, or what not.
a car / truck, you may drive 5 minutes to a few hours without ever really needing to shift a gear. but for tractor. *shakes head no* maybe for mowing a few acre yard (5 plus acres) and you just turn never slowing down. but tractors they are stop, go, stop, go, reverse, forward, stop, go, reverse, constantly all within a couple hours.