Can't figgure out how to search this one, so I thought I'd ask...

I'm flying a CO ticket on NW metal and I could not pick seats from the OnePass website so I went to NW and was able to enter the confirmation number and pick exit row seats. The seats show up on NW, but I get "-" on CO's page.

My question - when it gets to be time to check in, should I do it with NW, or CO? Will it make any difference?

TIA

DLM