It really depends on the type of river or lake bed you are anchoring in. For sand, small rock, mud or grass the box anchor is great. Also the box anchor is by far the easiest to store on your boat since it folds up and comes with a nice storage bag. For quick anchoring and easy adjustment add the anchor buddy to it (45' rope that has a bungie inside of it and shrinks to 15'). You can also get the shore spike to tie off the back of your boat to keep it square with the shore. Check out their website here, lots of handy stuff.
http://www.slideanchor.com/ Here is a great web site with the differant kinds of anchors and the applications, however it does not include the box anchor.
http://www.boatus.org/onlinecourse/ReviewPages/BoatUSF/Project/info5e.htm (Message edited by bkman211 on March 21, 2007)