I you want one, you're certainly intitled to it ; but I couldn't agree more with the other posts...parts are nearly impossible to find! I know a guy north of us that had one, and he waited over a month for a part! If you get one, I suggest stock-piling everything you're gonna need, plus a little more..
The sad thing is they only break when you use 'em..
I want to make sure you are getting accurate information off this forum. You experts out there, correct me if I am wrong, a 4425 is an upgraded domestic 4400, so parts should not be an issue. A 4435 is an imported German model, which would be problematic for parts. You should be ok with a 4425.
The 4425 is also the German combine. The 4420 is the updated 4400. I would definitely NOT go w/the 4425 or 4435 for the reasons already stated and others to numerous to mention. a 4420 has a few creature comforts the 4400 didn't have (hydraulic unload auger fold), but other than that is pretty much the same. I'd go for a low hour 4400. Happy shopping!
I wouldn't mess with a 4425 or a 4435. My friend had one and it was only trouble. Always stayed broke down and couldn't get parts. If i was you i would take the money and try to find a good used 6620 still small and a lot more combine, and it is a lot more dependable combine.
I bought my 4420 for a guy why traded for a 4435 and from what he has said the 4435 is all german built but the 4425 has a american motor with german everything else. He said both has less moving parts than the 4400 or 4420. He ran my wheat with his 4435 this year andit is a nice machine. I don't know anything about parts becasue he has not had anything break yet. it is a lot nice than my 4420 on the inside and can run a lot faster with a 15' head than my 4420 would ever dream of doing. its a hydro and turbo charged with a lot more HP. I wish my 4420 was a hydro but i got lucky and it does hav the auto float for the grain table. I woul hate to own someting I could not get parts for. I can get almost anything for my 4420 within 2 days a week at the most.