Comparing super zoom lenses is really not very much different then comparing any other lens. For super zoom lenses you need to understand that in general they are all based on compromises. The big three that you will have to choose between are optical quality, size, and price. Typically you get to choose either 1 or 2 of the 3, but not all three.
Size, weight, focal length range, maximum aperture, optical quality, build quaility, features, and price all are factors to consider, just as with any other zoom lens. Do you need the absolute best image quality available as well as the largest focal length available as well? Be prepared to spend a great deal of money as well as have a phyically large lens. Do you need a lens that is a reasonable size and priced on the budget side? Prepare for less then amazing image quality or a very small focal length range.
Some of the specific things to consider when selecting a super zoom lens include:
- Focal length range
- Variable aperture values over the entire focal length range
- Optical quality especially at the focal length you plan to use most
- Overlap with your existing lenses