I have used both and yeah - for me it depends on the doll. I don't care for fake fur wigs at all, but I love the look (and feel) of a true mohair wig (I've bought several from Carrie/Tinybear) and currently am holding onto a special commissioned wig in the hopes my upcoming doll will love it. They are versatile and natural looking and surprisingly easy to care for.
I also love synthetic wigs and most of my dolls currently wear them. I pretty much stick with Leeke World wigs although I have bought wigs off the MP from unknown makers.