As a sometimes seller and more frequent purchaser -- quality. Show type with good conformation and prestigious breeding from a reputable, successful breeder is what gets my attention and business, and it's what I've been able to sell quickly in the past.
To me, the training is just not even a factor in most cases. I can't think of any miniature horse I bought in the past 10 years with the exception of one where prior training mattered to me. The quality, show potential, bloodlines, and breeding potential have mattered to me.
Since they make good horses every day, I also factor color into what matters to me. It makes up for NOTHING, but if all else is as I like it, then cream dilute is a plus for my herd.