I went with one card for simplicity and flexibility, an Amex charge card (Plat in my case).
MR points are the most flexible for me but my biggest one is that they don't expire for any reason. Others have 18mo limits, 1yr, whatever.
You can book with Amex and pay with points, any airline, you can transfer points to miles for a small hit (a fair amount of airline options) etc.
With (for example) an AA Citi card, as far as I can tell, those points are good only for whatever, and only, what AA offers.
Last edited by danpass; May 2, 2012 at 11:42 am