Need Mileage Program Suggestions!
 

Current UAL MP Balance - 28,702
Current Delta Skymiles Balance - 6698 (Million Miler- 8625)
Current AAdvantage Balance - 15,000
Current FlyI Balance - 1400 points

Base City - SDF or CVG, both are equidistant from my location.

Frequent travel to EWR, once/twice yearly flights to LHR/LGW, and semi-regular flights to RDU.

Looking for suggestions on an airline and mileage program to shoot for while banking segments/miles doing corporate travel.

Thanks for the help!

Beware OF AAdvantage
 

Beware OF AA. They keep making it more difficult to redeem. Noe they charge $250 to upgrade plus 25,000 miles

Well, looks like you have all three alliances wrapped up (United for Star- US, Lufthansa, Singapore, etc; AA for One World-BA, etc; and DL for Skyteam- CO, NW, AirfranceKLM, Alitalia, KE, etc) and a LCC (Indy air) so you're all set in terms of number of FF accounts.
From CVG, you could focus on Delta if you don't like connections as DL will give you the most options.
But at any rate, AA, UA and DL all have some form of elite-status fasttrack or challenge, so if you plan to fly something like 10,000+ miles not on extremely cheapie fares in the next 3 months, check out their respective threads for info. Good luck!
Oh yeah, one thing I like about DL is free unlimited upgrades (when available) for elite members. But all four carriers are great...choose based on route schedule I suppose.

I'm not sure I'd agree that all four carriers are "great," but I agree that the differences aren't big enough to make that a reason to pick one over the others unless all everything else is nearly equal.

In your case, they're not. You're near one of their hubs, DL's at CVG, and not near a major hub for any of the others. Unless you enjoy the prospect of being forced into an extra connection any time you go nearly anywhere, that (for me) ought to settle it.

(I often make voluntary connections for extra miles, time permitting and fares being about equal, but that's not the same thing. I want it to be my choice, not a requirement.)