The newer one is a "Troy-Bilt", and that's the one we use for the lawn. I installed a bagger on it so that we can compost the grass clippings. I don't like the Troy-Bilt very much, because the Forward/Reverse speed is controlled by a lever that you operate with your left hand. When you need both hands to spin the steering wheel, that doesn't leave a hand left over to control the speed of the mower. I wish it had a foot-operated speed pedal. That would be more sensible.
This spring I happened to be out in the shop one day and happened to smell gasoline. After a long search, I found that the Cub Cadet had leaked a large puddle of gasoline out the air filter, draining the entire tank to the floor. It would have been ugly if the shop heater had decided to cycle at that time. Next winter season I drain all the fuel tanks!
The Cub Cadet is the field mower, and I got a lawn mower repair education from it. The mower deck was destroyed, so I bought a new shell, new spindles for the blades, replacement blades, and a new set of belts. The process was pretty complex, but I was able to swap all the equipment over to the new shell without screwing it up too much.
Next I had to do something about the fuel issue. Clearly the carburetor had a stuck float. I wasn't sure if fuel had filled up a cylinder and/or leaked into the crankcase oil. So I took the carb apart, cleaned it, and changed the oil. Not a bad idea to change the oil every season anyway. Also had to replace the battery, as it was toast. Should have kept a trickle on it... Oh well.
Afterwards, I took the Cub Cadet out and mowed the forest out front of the house. Thing ran like a champ aside from throwing the drive belt a couple of times when sticks got up into the housing and pulling the belt off the pulleys.
The mower deck took most of an entire morning to get all the parts swapped over and adjusted. The carburetor took only about 30 minutes to fix.