Credit line transfer

Hi there, I have the Venture and the Venture One. One of my other cards got upgraded and I didn’t realize it was similar to the Venture I already had.

I want to transfer my Venture one credit line to my Venture as the Venture has better rewards/miles.

Question is should I leave $500-1000 on the Venture one or should I transfer the entire limit? I don’t want the Venture one card but don’t want to close it and get my credit score down…..

Thoughts welcomed! TIA