I had a few discussion about balancing beads like this previously as well...

Anyway, I had been down at the 2005 World Tire Expo and I spoke to the Presidents of both Equal and Counteract and I have to say I think that Equal seems to be more popular because it is the older product in the market, but that counteract has a better product for a few reasons.

1) Counteract doesn't clump nearly as bad as others do when wet and due to the shape of the particles and also dries more quickly (Counteract did a test against Equal and Magnum and Counteract provided the least resistance when wet....thus it is also most efficiently distributed even when wet).

You can see a comparison of what each looks like here:
http://www.counteractbalancing.com/compare.htm

2) The real secret to the advantage of counteract over Equal is that Counteract creates more static charge than Equal (you guessed it, again, composition and shape). He told me that they are not able to publish this because Equal sued them in the US and got a court order against them such that they are not allowed to use that fact as part of their marketing (but it is a property you can clearly see in the product displays) and can be fined for mentioning it to US citizens (he thought I was a Candadian so he told me ). What this does is to supposedly slow the shifting of the material and reduce the material from having to completely rebalance during acceleration (ie you may feel a momentary shake while it shifts inside as you get up to speed with Equal before it smooths out).

The counteract sales director said he would get me some free samples to try for my truck so I will report back after I see how well it does. He did say that "less is more" when balancing tires and you shouldn't need more than 3-4oz for even large passenger truck tires (that way you get maximum advantage from the static property and little excess material movement) and that should be fine for both on and offroad use. He said that they are working on a product for low profile tires, but he said you should use the "Counteract Balancing Beads - Truck Product" for SUV's, pickups, vans and tractor trailers with normal profile and oversize tires. He said retail it goes for about $13 a bag (comes with a special valve core and step cap too) so not too bad for a set of tires but said you can find it for less from dealers.

Funny part is that both claim to have never been taken up on the performance guarantee to refund the purchase price if you are unhappy with the product. They both also joked that you can use sand or gravel and it does work, but it will eventually wear through your tire and rim....definately ghetto and cheap tho.