Where a drywall sheet joint meets an outside corner, is it better to first install the tape over the joint or the metal corner bead?
My old drywall finish guy did tape first, I think, but my new guy wants to do corners first. For me it makes sense to to tape first so that the tape is tucked under the bead.
Most tapers place the metal corner bead first. This is primarily because if you were to do any taping first you'd have to wait until that dries to install corner bead. It's a matter of efficiency.
It's also usually best to keep metal bead set snugly to the drywall, with nothing behind it. This allows you to keep it straighter and on plane. It should protrude just slightly on both walls when a straightedge is set against the drywall perpendicular to the bead. "Tucking" the tape under the bead does nothing of value. There's tape all over the building that's not tucked under anything and it's not an issue.
All that said, drywall taping is something of an art and you're free to do what makes sense for you and your project. Just remember the cardinal rule: lighter is better. The pros I've worked with do very little sanding to produce fantastic results, and it's far easier (and less messy) to skim on another coat than to grind down humps.
The corner bead that I use is pre taped. Put mud on the wall and push the bead in and work the mud out and over the tape. If using the bare metal anchor with screws then mud and tape. Putting tape under the corner bead will make it bulkier and not have a nice crisp corner.
Mechanically attach metal corner bead to the drywall or framing with staples or nails. Next put sticky mesh tape over the metal to drywall transition on each side, then fill will all purpose joint compound, let dry, then put lightweight joint compound over that.
