While neither are my favorite lender, they are by no means my worst either. My discover started off as a $2k student card years ago and has grown quite nicely. I have never had any issues with customer service, but I don't call them much. I like their 5% categories and that is about all I use it for.
Cap One treated me well so I have no ill will toward them. My only "gripe" is that a CLI was hard to come by, but I was given a 30k starting limit and didn't use it a bunch so I can see where they are coming from.
Amex Delta Platinum 20k | Amex Hilton Aspire 20k | Bank of America Premium Rewards 21k | US Bank Cash+ 25k | Chase Amazon Prime 25.3k | Lowes 35k | Barclaycard Aviator Red 40k | Chase Marriott 50k | Discover It 50.3k | Thank You Premier 52K | EDP 56k | Bank of America BBR 78.9k