Ok, I went back and looked at Warmack against LSU, TN, and ND and then Cooper against Duke, Maryland and another I can't seem to remember now.
First the level of competition in a good bit different although ND looked more like the AC level. TN wasn't bad nor LSU. Maryland much better than Duke. I think the other team was VA or VT?? Noticeable difference between the SEC and the ACC.
Anyway, Warmack is definitely better than I thought but he's still slow. His strengths are mass, strength, power blocking and he's actually quite good with his skip block. He's ok with pass protection but he gets too high too often. He's so strong he generally still anchors well. He is not that mobile and he is not going to do a lot of pull pass blocking at the NFL level. He does not move well downfield nor does he block well at the second level. Not at all but if he gets his hands on you then that's it. He's not going to be able to do screens. But his skip block is very good. He works well in close quarters and his feet are good enough there to be effective. Put him in open space and it's a different story. Forget open field blocking where he lunges and still is ineffective. His zone blocking is pretty good BTW. I thought he did ok right or left.
Cooper does not have the mass and strength of Warmack but he's good for his body type. He has room to add some mass. His feet are very good and he moves well pulling to either side side including pulling to pass block. He is very good in space NFL ready there. He can get to the second level easily and he even gets beyond that and moves very well for a big guy. His power blocking is ok to good and nothing like Warmack. His zone blocking is better than Warmack but he does slide off defenders some which Warmack doesn't. He has adequate power in the ZB. He anchors well and generally gets good bend, extension and has a good base. He just isn't as strong as Warmack in pass blocking but he's much more mobile and keeps in front of his guy mostly. He leaves his feet too much pulling esp at the second level. He's going to have to stop that are they will retaliate eventually.
They are two different kinds of players and I think Cooper has more room to improve. I think Warmack is just going to improve with some footwork, bending and anchoring better. He stands up at times. He's NFL ready although he'll improve some over a year or so. If Cooper gets stronger and more massive without losing his feet and mobility then he can be special. He does not have the butt or thighs like Warmack and likely never will.
Both are ready to start although Warmack is more ready due to his strength and drive blocking. Cooper will be the better pass protector and be more versatile for Garrett's offense.
You choose.