Mark - welcome!!!!!
129 vs. 1250 is a tough question. Both are 12hp hydrostatic drive tractors. The 129 is part of the 1x8/9 series that was built approx. 1972 to 1974. The 129 had the Kohler K301A engine bolted directly to the frame. The 1250 is part of the Quiet Line series built between 1975 to 1979. The Quiet Line series had IH first "full enclosure" engines (full side panels) and the Kohler engine was an AQS (Q for Quiet) with a special cooling air flo design and the first time IH used a rubber iso mount system. The Kohler AQS engine in the Quiet Line also used an integrated starter (bendix style) while the Kohler engine on the 129 had the A/C Delco belt drive stater/generator.
The hydrostatic drive utilizes a Sunstrand pump and is basically the same on both tractors except for the control handle and a rubber driveshaft rag joint connector on the 1250. The 129 has a left hand hydrostatic drive handle while you steer with your right hand. The 1250 Quiet Line has a right hand hydro control lever while you steer with your left hand. I tend to like the Quiet Line right hand hydrostat/left hand steering probably because the very first CC I had was a 1450 Quiet Line. You'll likely get used to either very quickly.
Now, Digger mentioned the 129 as being easier to work on and I tend to agree. Most of the engine is fairly exposed and easy enough to get at if you need to do any work. The Quiet Line 1250 has the full enclosure side panels that you have to remove to expose the engine, and it has an enclosed muffler box and a fire wall next to the gas tank, all of which makes getting at things a little more difficult - but I also agree with Digger about liking the Quiet Line style tractor. When it's all closed up with the side panels it sure makes a nice looking tractor.
So - your question was "which is the better tractor in general". My answer is they are really both about the same tractor and there are pluses and minuses to both. You didn't mention if there was any price difference. If there is that should certainly play a part. You mention a rebuilt deck on the 129. If the deck has been completely gone thru that could be a big plus - but you don't say anything about the deck for the 1250. In the end, since we cannot see or hear the tractors, I would suggest your decision should come down to which you believe is the better tractor with the features it has and the decks or any other attachments. Digger mentioned Hydraulic lift. If either tractor has it that is certainly a BIG plus and I'd definitely go towards the tractor that has it. (You can add it to either tractor with a fair amount of work but you have to find a donor tractor that has the correct set up).
Hope this info helps.
But the 129 is easier to work on.
