Depends on your location.
Are you in a valley? Or on top of a hill?
If it is level land around you then any .625 or .64 wl will perform good.
If you are in a valley and need a high angle of radiation then a 1/4 wl will provide that.
I have tried the .64wl antennas. Aluminum, fiberglass, etc.etc.
I have found there is no "BEST" groundplane.
I currently have an antron99 on top of one tower at 65' to the feed point.
It works 10.11.12, and 15 meter bands without an antenna coupler.
The other tower is the imax 2000 at 80' to the feed point. It also works 10.11.12. and 15 meters without an antenna coupler.
For around $130 shippd to your door it is hard to beat an imax2000 for the money.
Wrap an RF choke at the feed point, install it as high as you can and start making contacts.
This link has 9 pages of reviews for the imax 2000, by amateur operators no less.
http://www.eham.net/reviews/detail/1376
another review
Imax 2000 Base CB Antenna Review