Let it be cash, points or miles, I don't think Discover is the best card in your situation.

I used to use Discover for cashback. As far as I know, Discover doesn't offer "strong" customer support nor good card holder extended warranty as other big cc companies (Amex...etc). They also raised the point redemption threshold recently (maybe mid-year?). Not the best cashback reward card in my book. I didn't use their miles program but I assume it's similar to Capital One, which is NOT as easily redeemable/ticketable as regular airline miles programs. If you have Amex SPG, that will give you more flexibility to transfer points into different FFPs with 25% bonus per 20K transfer.

You may want to check out these threads and sort out what's best for you:

Frequent Flier Credit Cards versus Cash Rebate Cards

Consolidated Best Rewards Credit Card Discussion, Hugely Comprehensive

The "What Credit Card Should I Choose?" Master Thread

Business Owners

Welcome to FT!

ps. If you decide to get Amex SPG card, lots of folks will be glad to refer you so both parties can get referral bonuses (just go to our S.P.A.M. Forum to ask someone to refer you).

ETA:
pps. See Happy's posts about ThankYou points. The return value isn't as good as it used to be. You should also visit our Other Credit Card Programs Forum to read more about Citi ThankYou Points in depth.