Maniac,

You could possibly earn more on the car(s) by renting National or Thrifty, getting points from HHonors at the hotel and miles from the partner airline.

And there are differences between how the partners in these programs, not just HHonors, work. For example, if you plan to exchange points to miles, AA does 1:1, while most airlines do 1 mile to 2 points.

Here is a link to my opinion on what are the best car and double dip opportunities for maximum points after converting miles or km to points. Remember that 1 km = 1.6 miles.

http://www.flyertalk.com/forum/Forum57/HTML/005327.html