You're not really comparing apples to apples. The 3400 and 4400 are similair but the 4400 is ceratainly a larger frame. I consider a 3400 a true compact. I classify the 4400 as a large compact. The MX is similiar in size to the 4400 but a tad larger than the 4400. I consider it as an extra large compact.
The 3930 is a true AG tractor in weight and capacity. If the prices were close on all the units you listed, then the 3930 is the winner hands down. I would not consider the MX5000 due to the 2WD. It's a light machine and without 4WD you're not going to be satisfied. I would purchase a 4400 with 4WD over a MX5000 with 2WD. Again just my personal preference.
If you are concerned about the condition of the 3930 get a mechanic to check it out for you. You could run a compression test on the engine and perform tests on the hydraulics. If the machine has had regular service 1100 hours is nothing in my book. We've got three tractors on our farm with over 4000 hours on them. Two of those units are gas burners. These units are made to last.
