Dave,
If you're using stained crown, a butt joint might look better unless you
can find two pieces that match grain and color close enough to make the
joint mostly invisible. Unfortunately homebuilders usually order me an extra
inch or two of crown and I just don't have the material to play with. When I
supply material, I make sure and order enough to make this happen.
Like I said before, in 21 years I've never been called back because a piece
of trim has shrunk. When running base do you mitre your inside corners as
well or do you cope? Just wondering. I mitre everything and glue with Elmers
or Titebond. Works well for me. I average about 7 minutes running a piece of
base this way. I 'm running a lot of short pieces I can make 80 bucks an
hour. Running long stuff, the best I've ever done was 40 an hour (that was
on a good day). Takes me about two minutes to cope a piece of 5-1/4" MDF
baseboard. If I have to run 300 pieces of base in a house I save ten hours.
Takes even longer to cope a piece of poplar.

Kevin