Brent,
I have a 4x4 5400. It is about the same as the 4900 you are looking at.
I would not get a tractor unless it was 4wd. I have had both. 4wd makes a huge difference.
Often is the time I'll be doing a task, let's say boxing my drive, and I'll notice I'm slipping a bit. I engage the 4wd and the difference is night and day.
The reason I'm such a big believer in 4wd is because about 3 years ago I got a 2wd Massey 135 stuck in some mud. I had been working about 20 minutes to get it unstuck. Not fun work. A neighbor came over and asked if I minded if he brought his tractor over and pulled me out. Mind? I was ready to get this man into the Sainthood. Anyway he come across the pasture a few minutes later on a little Kubota tractor. Not to put anyone down, but I thought it was a lawn mower. I laughed and told him I didn't think he could help me. He insisted. Guess what, that little thing was 4wd. It pulled me out without too much of a problem. Now my Massey wasn't a big tractor, but it was a tractor and his little Kubota humbled mine. I swore then and there that my next tractor would be a 4wd Kubota.
My Brother bought a 3710 HST 4wd. Same thing. He'll be doing a task, slip, go to 4wd and no more slipping.
As to what's better, the L series or the M series, depends on what you are using your tractor for. Let us know.
Bill Cook