As for Capital One, only the Venture Card earns 2x capital one miles. The regular Capital One cards and regular (non-venture) Capital One rewards program is a lot worse than Citi ThankYou points. You can get $50 gift cards for 7500 points, worse than the 6000 points needed in the ThankYou network.

But I suggest that that the OP use his personal rewards card for business transactions (if his company allows), so that he's not paying an additional annual fee. I don' think $75 for the ThankYou program is worth it for only $10-$15k in annual spend. Makes much more sense to consolidate rewards. You can't do much in a year with 15k TYPoints.