Gary,
The big difference it the frame and transaxle. The 1440 is a Cub Cadet "Cyclops" Garden Tractor. It is more akin to a 82 Series or like like an 1811 style tractor. It has a full channel frame that extends the entire length of the tractor (much like the frame on a car) and the transaxle, and engine mount "in" the frame. The transaxle is the aluminum version of the IH style transaxle, and capable of running ground engaging attachments. Like a moldboard plow, tiller, disc, cultivator, and a large snow blade or snowthrower/blower
The 1420 is a Cub Cadet Lawn Tractor. It is more a kin to a riding lawn mower from a big box store (or that place outta Chicago that is slowly dying)... it will have a lighter frame that is much lighter steel than the Garden Tractors. The frame reminds me more of a shelf that everything is mounted to. The engine and trans-axle are mounted "on" the frame. The trans-axle is a much lighter duty unit, that can only really handle mowing and something light like a lawn cart, maybe a sweeper or small roller. Nothing ground engaging... they did sell a snow blade and maybe a snow blower.... but this use does shorten the life of the machine.
The 1420 is a lawn mower.... nothing more really. Not saying it's a bad machine, but it is limited in what it can do. But, you don't have to stop at one... keep looking and pick up a garden tractor also. Most of us have more than one tractor. Or some, like myself, I have a new CC ZTR, and several older Cub Cadets. The ZTR does an awesome job cutting the grass, but any other work, one of the tractors comes out. I won't even pull a cart with the ZTR (the hitch hasn't even been installed), I get the tractor out. This time of year, the ZTR is tucked away in the barn and the 1450 is in the garage with blade on it.