Crown/Overlay options

I have two molars which are cracked. One had a large amalgum filling, the other is still in my mouth. No pain. My old dentist just said to let them be if they aren't bothering me.

I switched dentists however. My new one wants me to get a crown on one and overlay on the other citing the preventative measure of doing so. This makes sense to me I guess, though I hadn't budgeted for this expense!

My new dentist uses a CEREC machine. I've read so many conflicting things on this vs. a gold crown/overlay. I'm curious what dentists actually think about the two options. These are in my farthest back teeth and I don't care about cosmetics, I just want the best bang for the buck. Something that's going to last awhile.