I smoke my corncobs mostly, this website has nice stems for MM corncobs, http://www.walkerbriarworks.com/html/_forever__stems.html
I have the "fire swirl 4-3/4 bent" - stem on a bent "country gentleman" Missouri Meerschaum pipe, it looks very cool imho. It is my current favorite pipe.
But, like most people will tell you, it is personal preference that matters. I like my briars and clays too.
I feel like corncobs and clays effect the tobacco less, but I readily admit I dont always rest my briars. If they sit a long time I dont really notice ghosting. I had Dunhill London mix earlier in a corncob, and right now in a briar that hasnt been used in a few weeks, I dont think I notice any difference.
I dont have any real expensive pipes, I think one of my briars was about 60.00. If I really splurge someday It'd be a really cool calabash I think.