I've gutted the shower/tub in my guest bathroom and need to replace the
copper piping. I am going to cut the copper as close to the slab as I can
and start fresh.

Do I go with copper again, or do I use PEX? Why?

A lot of the PEX fittings (it seems to be the quicktite ones) all say to not
be used behind a wall. Can I use PEX with crimp fittings behind a wall?

Do they make an adaptor that lets me go from copper to PEX?

I don't own a crimper and havn't worked with PEX, is it something I can DIY
if I buy the proper crimper and parts?

Evan Mann wrote:

I've gutted the shower/tub in my guest bathroom and need to replace the
copper piping. I am going to cut the copper as close to the slab as I can
and start fresh.

Do I go with copper again, or do I use PEX? Why?

A lot of the PEX fittings (it seems to be the quicktite ones) all say to not
be used behind a wall. Can I use PEX with crimp fittings behind a wall?

Do they make an adaptor that lets me go from copper to PEX?

I don't own a crimper and havn't worked with PEX, is it something I can DIY
if I buy the proper crimper and parts?

I would go with copper. Buy a (small) roll of 1/2" Type L soft copper
(5/8" OD).
It's excellent for bending to fit in tight places like you have.

To avoid having to solder right next to the shower control, make up
some short stubs with male adapters and screw them into the control.
Then you can solder couplings between the stubs and your Type L risers.

Jim