Most people never take the time to set up their miter saw to get it to
cut correctly. You can adjust fences, stops, tilts, etc. on just about
all of them, but almost no one I know takes an hour (or two) to set
their saw up correctly.
I have a 12" Rigid that I use for decks and the like, and it is OK.
With a great blade, you can do some really good work after tuning even
on large, painted crown molding.
My 10" Delta never would "get right". I worked and worked on it with
my engineer's square, and no matter what, I couldn't get it
satisfactorily square. Close, but no cigar. So... OK for baseboard,
decks, door trim, etc.
My 8" Delta is a great "handy" saw, and is super for running small
house trim and shoe molding. It will match it own cuts as in a scarf
joint, but will not, cannot cut square. After using it for the last
few years off and on I am sure that never was a design concern.
My 10" DeWalt is actually one of the few DeWalt tools I like. I came
reasonably square from Taiwan, and it has plenty of adjustment screws
and room. However... the right side of the pivot base on the one I
bought was around 1/64" out of whack no matter how I tried to square
it. Finally after adjusting, testing, aligning, etc. for about two
hours I went to my shop and got a large wood mallet, set a 2x4 across
the offending offset and smacked it a couple of times.
It is now square, I am happy to report. It will stay that way until
someone knocks it over, or jams it up when they let the material move
while cutting, or forgets and tosses it in the truck bed at the end of
the day instead of in the front seat with me.
Once I got it squared to my satisfaction, I don't let anyone use it at
the shop or out on the job unless it is an emergency.
BTW... I never have seen a dual bevel that you could get nicely squared
on both sides of the blade. Some are better than others, but none seem
to be great.