Depends on what you get and what your layout is like.  I have an older White, 54", not the big heavy ones like most have today with the bigger tires, I'm sure they're much better... mine won't hold grade on much of a slope, because of wheel slip.  It DOES cut your time down, even with a smaller one, because you gain all the time you were swinging out and turning before on every pass, now you're doing it in 1/5th the time each lap.  Can't beat them for circling around objects.  Mine just slips real bad on the banks in front of the house, I have to go up, going sideways it'll just drift down, and if I slow the uphill wheel to hold the front end up, the low side one just wants to drag it along at whatever speed it's spinning at and then it breaks loose and the whole works will slip downward and tear up the grass.  A bigger machine with better rubber probably doesn't have that issue.