I have a 20" push and a 42" JD rider.
When the 42 was bought for $500 more it would of come with a 48 deck.
Wish we had because I saw that the extra 3" the deck extended on each side would make trimming easier. Also when the gass is extra thick in the spring I have to overlap half the cutting deck width sometimes to get all the clippings all mulched up so their not visible. That extra width would cut that double cutting time down.
But everyone has to make what they have work.
I have some props where the 20 is all that will fit in certain spots. And is better then cheating with a line trimmer in those tight areas because all to often a trimmer will dig in and scalp the lawn in spots.
Thing is my next mower maybe a 36 to get through the small gates. Right now I only had one prop this way. Lucky that back yard was not that bad to do with a 20, it was not that large and flat .
Also a 36 and my 42 used together would increase my productivity on the larger properties. Also I have avoided steep properties because I can't use my rider and I'm not going to be pushing my 20 on those hills. Legs are not that young.
Thing is my trailer needs to be replaced with a larger trailer before I go to larger mowers then my 42.
My point is it's always best to use what you have first, buy what you can afford second. Stay out of debt.
Where I live most gates that are installed now are 5' so a 48" should get through. Though there are many smaller gates around.
I have a property where my 20 never gets used because my 42 fits everywhere.
I have only one place where I could do the whole yard with a 60 if I had one except for using a 20 to just get around and under some shrubs.
I would not trade in your 48 for a 60. I would keep the 48 for a back up for the 60. Then have both available if you got some sizeable properties to do.