You must be an accountant to do all that research!

My $.02: If you live in Chicago, I would definitely go with United. You will get so tired of connecting thru CLE, EWR, and HOU on Continental to get anywhere. UA has so many direct flights from ORD. I know this goes against the flyertalk credo of mileage maximization, but having spent the night in many airports, I can assure you, it is not fun.

With your flight schedule, if you get the United Platinum Visa with its bonus EQMs, you should be 1K by the end of the year. You might have to do a mileage run or add on a few segments to your business trips (take US thru CLT for example), but it should be easily done. I love flying UA as a 1K.

If you're just expensing this to your company, you do not need a business Visa. I don't think it would matter other than the biz card balance wouldn't show up on your personal credit report, but it would be paid off every month, it might improve your personal credit scores, so you may be better off using personal cards.

For hotels, I am a Hilton guy only because I think the Homewood Suites is the best hotel on the planet for staying on a weekly basis. And there are far more Hilton than Starwood hotels. That being said, I do have both the Hilton Amex and the Starwood Amex, just in case. While I'm sure I'll get crucified for this, I've never stayed at a Marriott that I liked. Just my personal experience...

I have not done a cost comparison, but an educated guess tells me that using hotel points for hotel stays is better use than transferring to miles. The only exception might be the 25% bonus when transferring Starwood points. With your flying, you'll have plenty of miles. Keep the hotel points and go on a free vacation.

Welcome to the world of frequent flying. Once you get hooked, you'll never want to fly without status again.