[sphelps]

Effectively all macro lenses are capable of the same magnification (1:1) no matter what the zoom. The difference is the minimum focus distance which is the distance from the lens to the subject to achieve this maximum magnification. For example a 60mm needs about 8" while a 100mm needs 12". I went bigger and got a 150mm which needs 18" because at the time I had a 36" cube tank so this lens allowed me to take true macro photos of anything in the tank.

So when choosing a zoom length for a macro the most important factor in my mind is this minimum focus distance, determine what you need and choose appropriately. As for brand I would recommend sticking with the same as the camera whenever possible.