That Kioti 45 hp. will be fine for the described use. Most 100 ac farms were maintained with smaller tractors than that just a generation ago. It should be able to pull about a 7' bush hog, unless it is thick grass over 4' tall. If that will be the case get a 6'.
by my math 100 ac = 4356000 sq ft.
at 5 mph and a 5' bushhog you mow 132,000 sq ft / hr
that's 33 hrs to mow it once ( not quite 1 wk, just 4 eight hr days)
at 5 mph and a 7' 'hog you mow 184,800.00 sq. ft. / hr
that's 23.57 hrs to mow it once.
I don't know how well you need it maintained but I only mow fields for brush control 2 times per summer.
As far as Hydrostatic goes, If he has been on a tractor most of his life he will probably be more comfortable with a shuttle shift.
Dealer quality is more important than brand.
by my math 100 ac = 4356000 sq ft.
at 5 mph and a 5' bushhog you mow 132,000 sq ft / hr
that's 33 hrs to mow it once ( not quite 1 wk, just 4 eight hr days)
at 5 mph and a 7' 'hog you mow 184,800.00 sq. ft. / hr
that's 23.57 hrs to mow it once.
I don't know how well you need it maintained but I only mow fields for brush control 2 times per summer.
As far as Hydrostatic goes, If he has been on a tractor most of his life he will probably be more comfortable with a shuttle shift.
Dealer quality is more important than brand.