I am completely sold on the Markins, because of the tension control, weight capacity and overall weight of the item. However, I haven't even bought it yet. I'm piecemealing my setup because of money, but my choice, given my lenses, the largest being the Tamron 200-500mm, is a Markins M10 (maybe the M20), with an RRS lever clamp. I have the RRS lever clamp attached to my Manfrotto 488, temporarily. Great quality clamp on a mediocre ball. I'm packing away money right now for the Markins. I know I'll be spending a bit more, but I just didn't see much advantage to a Markins clamp. All this is set up on the Manfrotto 3001, but I'm not going to upgrade that just yet. It's a money thang. check out
http://www.nikonians.org/html/resources/non-nikon_articles/markins/index.htmlI'm relatively new to DSLR photography, and the learning/equipment curve is huge. But, I'm having fun, learning an amazing amount, and looking forward to Spring. I know winter is good for shooting, but I hate the cold, and right now I have the flu, so shooting will just have to wait. My latest shoot resulted in only a pic of a European Starling, the bird we all love to hate.
http://www.pbase.com/di/image/73824869/original