Well, first of all, I am biased, because I chose the Scag Freedom Z. It was also more mower than I needed, but the dealer had an older model in stock and gave me too good of a deal not to pass up. I came here like you for advice, and ended up choosing that one.
That being said, I know several folks with the Liberty mower, and after at least a year of ownership there, they have no complaints. In fact, another co-worker just bought one last week.
Scag really hits a mark with me, because all of their components are made in the US, with the exception perhaps of the engine or tires. They may be as well, I'm not for sure.
The Liberty comes with a nice Kohler engine, and the 2800 series transaxle, which should last nearly forever with residential mowing. The back bumper on the thing is sick, lets face it. They also come with a 5 year, 5 year warranty, or 750 hours. I have used mine for 2 years on 1 acre and just turned over 13 hours. 2 more mows and I can do the first service, hah.
The deck does well in wet and dry conditions, and with or without the flap on, it throws grass well. I left mine off for a while because it was so large, but I ended up putting it back after I covered myself in grass too much. It does make a difference.
The only issues I have had in fact were my seat safety switch connection. Every once in a blue moon it won't start, and I simply un-clip the plug and plug it back in, then fire it up. They filled the plugs with the anti corrosion grease, so I think that inhibits connection if conditions are just right.
I also noticed that Scag's accessories, like the bagger or mulch kit, is probably some of the highest in the industry, so if you had your heart set on a bagger or otherwise, might wanna do the math.
Now, as for the Kubota, heck of a machine. I haven't done my research on them, but I have some commercial friends who mow with them, and they love them. They seem to hold up well, and meet the demand. It appears to have an upgraded transmission compared to the Liberty, but thats the 48" Komander I'm viewing. Headlights and suspension seat come standard too. Color wise, your on par either way with the orange, but it's going to come down the specific models and a comparison to make the decision.
Either way, I don't think you will go wrong. Here's wishing you 10% off either way. Maybe you will be the 1000th customer, etc..