Eeek..I don't want to beat a dead horse, as the one combine vs. two combines "thing" has already been discussed, thoroughly!
I am of the opinion, still, that two combines (their size equaling, together, the one big combine's size) are better than one. If one combine breaks , the harvest goes on...and when one combine breaks (when there's just one [big machine] in the field)...well, we all know that things are ~shut down~....
That being said, I would trade the 1688 for another 2388, if you need to get done faster (or whatever the case might be for "need"). (2) 2388s are gonna' get a LOT done in a day! Just keep 'em rolling!
The 8010, though, is a good machine, from what I hear and from what I've read. There are not any of them around these parts. One would have to get up around Dalhart, Tx to see those "beasts"!
Please let us know what you decide.