Well I own Both Deere's and Cub Cadet's several of each. I would go with The Cub 3100 just because it a full fledged Garden tractor more comparable to the Deere X700 series.
The GT3100 can take a Cat 0 3point hitch,42inch Hydraulic tiller, 54inch dozer blade,45inch two stage snow blower and even a Bucket Loader if you so desire. I would not worry about those Hrs on the Kohler 470hrs is fine that engine will last alot longer than that it a commercial Kohler engine a Kohler Command. I have several Kohler engine on machines that are 30 to 40 years old and still running strong. I personally for 1.5 acres would atleast use a Garden tractor to take care of That size Property. I have 5.5 acres myself and use a JD X485 which is the same as a Deere X720 for my main tractor. That 44inch deck will leave a Nice cut on the lawn You will not have the problems you had with the JD L120. The Cub Cadet is the best Deal for the money.

Here is a link that might be useful: Cub 3100 Spec's

Which one offers better service after the sale in your area?

Metal - These are all sold from 2 large reputable dealers in my area (both within 5 mi).
The new X300R has a 3 year warranty.
The 07 X324 has a warranty until the end of September.

sergeant - Thanks for confirming the Cub is a good garden tractor.

FYI -
I am thinking about getting a Johnny Bucket for the mower/tractor next year. A tiller would be really nice too but they are pricey so it is unlikely. Besides I still have an old sears roto-spader that just won't die.

If you are mainly going to mow I would get the GT245 with the 54"deck. If you "need" a heavy duty Garden tractor, get the Cub, otherwise you will just be hauling around extra weight, because you think somewhere, somehow, you just "might" need it.

I checked out the Cub Cadet 3100 yesterday. It is in rough shape. The last owner beat is hard (the front wheels were bare and I have never seen such all around ware in a young tractor). So I'm going to look at the Deere models tomorrow. I am now leaning toward the GT245. The Cub dealer also sells Kubota's and the TG1860G they had looked really nice but I read in reviews the belt drive and electric system had problems + the price is high (3700).

I have a 2002 GT245 and, as a mower, it does a fine job. The 54" deck cuts beautifully, especially with the Power Flow system. And it is fast..... very fast. Perhaps not quite as fast as one of those nice Exmark ZTRs, but close.

The Kawasaki 20 HP engines have had a few issues. Mine is no exception. One was caused by water/dirt getting in the tank due to a disintegrated rubber grommet. Another was caused by the dealer installing the wrong air filter, causing plug fouling. Both problems were detected and fixed by an independent shop. Otherwise, the machine has been bulletproof.

Adam,
I have about 1 acre and went from using a custom built reel mower to the X300r. I wanted a riding mower and more importantly, I wanted a great look without the big side-discharge bagging system. The X300r has turned out to be a super mower. My wife likes mowing the lawn because she doesn't have to try and lift off the bags...you just pull down on the lever and they're gone. It goes faster than I need it to and I can do my 1 acre in about 35 minutes (including the dumping). I can't speak toward the other mowers, but I can say I'm very (VERY) happy with the X300r.

cohiba767 - Thanks for sharing your C300R experience. I have a few follow-up questions. Are you mowing a full acre of lawn or is it less due to house/driveway/etc? How may times do you have to dump for per mowing?

FYI - The GT245 is now sold too... I found a few other tractors I thought were good deals and they sold... The local used inventory seems to be drying up.
On a positive note I sold my dreaded L120 for only $350 less then I had payed for it 3 years ago. And I just found a GT275 (~1996) with 48" deck and no hr meter for $1250. I'm going over to look at it now and if it is in good shape I think I will bite.

Adam