Car rental.....Hotwire or Priceline

I've got reservations with Budget and Alamo. I always have a backup.
I was considering trying Priceline or Hotwire. I would like to rent from the top 6 rental car companies. Do either of the two above guarantee you a rental from a well known company?
Thanks in advance?

Hotwire does, take a look at their website. I have used them five or six times mostly in Florida. The times I have used them I have saved a lot of money. You post the dates you want the car and have them do a continual search. They will email you the current rates from time to time. You will get that info right up to trip time. Sometimes last minute rates drop a great deal and you can grab a great bargain.

Both priceline and Hotwire will tell you the total fee. I start with Hotwire, and then frequently go to priceline and submit a bid that has a total cost about $2 - 3 per day cheaper. About 1/2 the time I save with priceline. The car companies have always been majors for both companies. For full size and midsize, we've gotten Alamo about 50% of the time, Hertz about 35% of the time and Enterprise about 15%. Both of these websites regularly save us 5- 6 dollars per day over the companies websites and over Expedia, Travelocity, etc.

Tip for hotwire. - If you type in pick up times of 10 am and return time of 9 am, (times are just examples), you may get completely different rates if you type in different pick up and return times. Doesn't often happen, but last time changing times by a half hour saved $4 per day on a mid-size.

Roy

These two sites are the only ones we use - a total of probably 50 times in the last 15 years.

Thanks for the responses. Appreciated.