It depends on the style. Here are some butt jointed trim.

Stock builder grade "Colonial" trim that is mitered is a relatively recent building development.

Miters are good if you like that look, probably mostly done because it eliminates end grain that has to either be part of the design or dealt with by cutting somewhat fussy returns on each exposed corner, so it often takes more work to do the kinds of nice traditional trim shown in the pictures above.

Miters in real wood are problematic because wood expands and contracts with humidity changes, inevitably opening the joint at the miter, no matter how many screws, biscuits or how much glue you apply. MDF is probably a better material choice if you want the mitered look.

My preference is to avoid both miters and MDF trim.

Ok I gotcha. What does the architect in this discussion mean by "Bisquited"? I guess glued, and screwed are obvious. Should trim be glued and screwed rather than nailed?

What are the advantages over just nailing the trim?

Thanks for the pics.

Biscuit joints.

Here is a link that might be useful: Biscuit joints

Hmmm. Very interesting. I have Butt jointed trim in this house. I didn't know that's what it was called.

I would venture to guess that it is not Bisquited.

Is bisquitting something you should expect?

Rwiegand--my baseboard and crown is poplar and is mitered. At the mitered areas it does pull apart slightly. Is that unavoidable?

Thank you for all of the good info!

Attached is an explanation and picture of why miter joints open up. The longer the joint the more they will open-- on a 3/4 in wide baseboard the cracks shouldn't be noticeable, on a 4-5 in wide casing they will be obvious.

I'd think screws or biscuits are unnecessary on trim that is firmly nailed to underlying framing.

Here is a link that might be useful: why miter joints open

That level of attachment is complete overkill. And probably counter productive unless all 6 sides of the wood are completely well sealed with multiple coats of paint or shellac. The normal cycling of wood can end up cracking something that is that tightly joined. Especially if the back side isn't finished and can still absorb and release the normal seasonal humidity changes.