I personally would have to give it to the older gleaners, the L & M series are tried and true conventionals that are still running today. You can buy an 83 L3 gleaner with 24ft wheat platform for $9,000 in my area. They work, have been tried and true, and keep running year after year. They are very cheap to operate and not too much to them.
You know, I'd vote for the Case IH 1660, but in terms of just IH, the 1680 is a much better machine. It has a larger diameter rotor that just seems to behave so much better. We used to run a pair of 1660s. One of our neighbors had a 1680, and just said is was a nice machine. It wasn't until we jumped up a size, that we realized how big of a difference it really was.
I don't really have the experience with the other machines on the list, so I'm going to stay out of he poll. My uneducated guess isn't going to help get correct results.
It has to be the 1660 but I agree with others that the 1680 is better. Also we used to have an old BM Volvo S950, that was a heck of a combine in its day-1967. It also has a very nice Volvo Penta engine which starts first crank even after being stood for 18 months, sounds real smooth bit like an IH 400 series engine, with a nice throaty roar!!!
1680 Every time!!!! or maybe a 2388.!!!!
I'd also have to go with the 1660. I currently own 2, an 86 and an 87, and harvested 4000 acres with them this fall. I harvested just short of 15 million pounds of grain in 05. I had maybe 2 hours of total breakdown time. One of the 1660's has close to 7000 hours.
It Hard to bet the tried and true 1660 I run a 2166 but my father still runs his 1991 1660 with little or no break downs. if it wasnt for a flat tire would have made it though harvest with no breakdowns.
I'll have to vote for the axial-flow. I truly believe the 1978 introduction of the IH 1440-1460 opened all the other manufactures eyes. These combines was comfortable to operate and was simple, with dependability. Very forgiving on settings also! They just kept making them better, and the 1660 was one of the best!
Axial flow all the way. For a cheap combine that is simple and reliable get a 1480 or 1460. We still run two and the do great. And the will eat up any L or M gleaner and spit it out. I used to be a gleaner guy as we had 3 G's but the Axial flow will out cut any combine from the early 80's, hands down.