Lapping with loose grit on glass or any other flat surface is great because it's cheap and easy, but it's also a mess to clean up unless you have a good place to do it. A DMT may run you a few bucks (no idea off the top of my head, don't remember), but it's fast, clean, easy, and will last forever. If you do it under running water (like in a sink with a flat bottom), it's no biggie to have the faucet on low. My DMT lives in the dish rack.

I have never had a diamond embed in any hone, and I don't see how it could. If the stone were soft enough to have a diamond embed, I don't think it would a) rip out diamonds nor b) hold onto the diamond during lapping. If you think the scratches from a DMT are too deep, you can easily rub them out with a slurry stone, barber hone, etc. Again, any hone that's hard enough to hang onto the scratches is probably a hone you'll only lap once.