Another topic has just been closed (rightly I think), leaving open this question.
As I understand it, small pool rewards are more variable but over time all properly functioning pools converge toward the mean, so focusing on pool size and ignoring other factors, only the fixed fee makes a difference. And it will obviously be higher per delegation if there are fewer delegators. But I’ve a feeling there is more to it than that, and there is certainly a discussion to be had on whether and when it makes a significant difference. Anyone with better analytic skills than me (or maybe just less lazy 
) care to chip in?