I have a 314 and a 317. Both are wonderful tractors.
The 314 is a little brute. The 317 hydraulic control valve and front coupler oil lines are a bolt in fix to upgrade the 314. The dual, independent brake pedal assembly is also interchangeable between the two tractors. Steering systems are also the same so if you find a Brantly power steering unit it will fit either tractor. Awesome mowing machine with H047 mower deck. I have a Ruegg 3PH on mine with weighted rear tires. With suitcase weights on 3PH and modified 43" blade on front I have used it to grub out tree stumps. The bad ... a lot of complaints about engine vibration. The fix for that is make sure you have good engine mounting isolators and low idle is set to spec which is higher (by sound) than most people like.
The 317 with either the Series I or the Series II engines are a good tractor. The lubrication system on the Series I get a lot of negative reports and publicity. The people who make these comments/reports know nothing about proper maintenance and service. There is still many of these tractors in the work force that are operating just fine. As another member stated you need to keep the crankcase full and watch the steepness of sidehills you operate on. Again, the 317 and 314 are identical tractors except for engine and parts are interchangable. The only negative thing I can say about mine was the lack of power steering. I now have Brantly steering units on both.
I'm going to get in trouble now. If there is a tractor to stay away from it is the 4X5 tractors (425/445/455). These have the Kawasaki engines (425/445) which I love. They are however the beginning source of plastic cam gear problem. So why didn't these get the same negative press as the 317 Series I. . Not only that but the plastic hood/shielding require you to refinance your house to replace them and they break often. And not by neglect or rough use. I was talking with a WFM member a couple weeks ago that has a 455 with snowblower. The heat from the exhaust system caused the lower front corner of the hood to break free from the rest of the hood. He agreed the cost to replace the hood was out of line and was going to design a change to modify the hood/mounting.
I've rambled too much ... Good luck with your decision ... Gabby