For the older ones without a doubt it would be an IH. Hands down were built heavier with the Farmall Cub trannies in them. Built them on the same line at the same time with the differences being the main shaft and the cover on the front. Any of them that IH ever made were near bullet proof. Probably why they are the most highly used garden tractor chassis for tractor pulling. They made a few lack luster models like the 1100, 482, and 582 special. The most sought after models are the 82 series. They are the pinnacle of what IH made and are awesome machines. We have 3 at the farm, an IH built 982 and 782 and a CCC built 782D. All three are great tractors in their own right.
Having said that there is also a 318 at the farm that mom and dad bought new in 87. When JD brought that model out is when I think they finally got it just right. From that model series of the 316, 318, 322, 332, 420, 430 and up till today it would be JD for me all the way. I think the only model before that thats decent is the 140. Throw a belt in the mix for a drive and to me it just takes away from what a garden tractor should be. I like a good old solid drive shaft instead. Having said that I somehow seem to have acquired a MF12 along the way here. Hmmmmm, not quite sure how that happened. I may need to investigate that, LOL.
When MTD bought the Cub Cadet line from IH and turned it into CCC they made good machines for a while. Up through the cyclops series were decent machines but after that I think the machines slowly went downhill to the point today they are really not that great at all. Many of them being nothing more than rebadged MTD machines.
So from pre 1984ish I would take any IH hands down. From then till now it would be a JD. I'm a die hard IH guy and if I went to the farm today to mow the yard and had to choose which tractor to get on, the 782 CC or the 318 JD. I have to say it would be without a doubt the 318. If I had to choose overall though it would be IH, the roots just run too deep and I bleed red not green.