IMO the best value really depends on what's important to you: the interest rate matters if you carry a balance (as you appear to do), the annual fee, of course, plus the number of bonus miles you get for signing up, whether it's important to you to have flexibility regarding how to redeem your hard-earned points (like with Diner's Club) or whether you're happy earning all your bonus miles on one airline.

If UA is your #1 airline, you might look at the UA Platinum Visa. I just signed up, and got 5,000 bonus miles plus a couple of UA coupons, plus they waived the $60 fee for the first year, plus the usual mile per dollar spent. That isn't an exceptional package, but it's OK. I got info about it from a link at http://www.ual.com

Good luck!