I've found the rental experience with
Alamo to be the best. I also have Alamo Insiders and usually book thru the Alamo site. The Costco code is mentioned above and the rate you get by going thru the Alamo site and plugging in the Costco contract ID and coupons is generally the same. Its pretty easy to find the coupon codes on the Costco site also. Going thru the Alamo site gives you the advantage of attaching your Alamo Insider ID, get the Costco rates and the ability to make any changes on the Alamo site.
If you haven't rented with Alamo for awhile, be sure to do the online checkin before you leave home - you'll give your drivers license and credit card info (you still won't be charged until you pick up the car). When you get to the airport, skip the Alamo counter and kiosks entirely -- just bring your printed online checkin and head out to the garage. Show your printout to an Alamo employee out there and they'll direct you to the proper row from which you'll pick your car.
The
Budget process is better than it used to be. If you're going with them, make sure you join their FastBreak. That way you can at least skip the counter in the airport terminal. You will need to stop at the FastBreak desk in the garage, but the line there is usually quite short...much better than inside.
I believe with both Alamo and Budget you get the second driver for free. You will be able to enter the second driver info during the Alamo online checkin; not sure about Budget. In both cases, both drivers will need to show their licenses as you exit.
One more thing: if you go with the automatic toll pay, Alamo charges I think $3.95 each day you use the toll + the toll costs, Budget charges I think the same (or maybe its $4.95), but each day of your rental, whether you go thru a toll booth that day or not. It tops out at about $20.
If all is equal, I'd go with Alamo...