The #1 problem I have seen with miter saws is the amount of play in the saw carriage. I have the bottom of the line delta 10 inch and it wonders all over the place unless I pull it down exactly right. check this out before you buy one, I have noticed that this can very from saw to saw in the model #
hope this helps

Rob

I'm not certain exactly what you are asking because both of those saws will
: cut an angle from the left or right on a 90 degree plane. It looks like
: one will also cut compound angles from either side. When I was doing lots
: of trimwork we always used a good quality miter saw that cut an angle from
: either side. The sliding, compound miter saw looked like it would be a
: good thing to have so we bought some. They worked fine, but setting up to
: cut compound angles sometimes took a bit of time...and even then the cut
: might not be perfect. We ended up doing 99.9 percent of the cutting on the
: original miter saws using our old tried and true by the eye method. The
: 10" saws work fine for 90 percent of everything we cut. For the rest
: we used a 15" miter saw. I guess what I'm saying is that the average
: person doesn't need a compound miter saw. Delta, Rockwell, Makita,
: Hitachi, and others all make pretty good miter saws. Stay away from the
: handyman stuff if you can.