Being a suitable donor has little to do with it.
I have the 3 IE liveried 071's and 077 is the better looking of the 3 in my opinion.
The factory weathering on 085 isn't great, and brings the model down slightly. 078 carries the smaller IE logo, which I like, but the majority who model that era seem to lean towards the larger logo.
You get the best of both with 077 which makes it that bit more desirable.