All depends on what your doing but I like the JD 4430 with a powershift. The 4430's steering, ride, and shifting are hard to beat for that age of tractors. That being said we did have a 1586 and it cranked alot better in the cold, frost on the ground with no either or heater. A 1086 IH would be a good one that you could get for less money than a John deere. At that HP range I would go with one closer to 130 HP over a 100HP just becuase at that hp there isn't a staggering difference between fuel use in that range unless you compare one right at each extreme of the hp range. Also the one with more HP would do the job more efficently instead of trying to max out a 100HP tractor's capability. Approximately 70% loading is where you typically get the best efficiency. I wouldn't shy away from a Ford 9600 if you can find one in good shape. My neighbor has an 8600, right at 105hp, that he has used for years with really good luck. The 9600 is just a step up in Hp from the 8600.
Good luck and I think you can easily find a good tractor for 15k. In the end I would go with whatever dealer is closer to you that has great service.
OldCrow