After playing around with macro photography on-the-cheap (read: reversed lens, rev. lens mounted on a straight lens, passive extension tubes), I would like to get further with this. The problems with the techniques I used is that focus is manual and aperture control is problematic at best. This limited my setup to still subjects (read: dead insects) Now, as spring is approaching, I want to be able to shoot live insects. I believe that for this, autofocus and settable aperture will be of great help.
So, one obvious but expensive option is a macro lens (say, EF 100mm Macro) However, I am not really interested in yet another prime lens. An alternative is the electrical extension tubes.
Except for maximum focusing distance, what am I losing when using tubes (coupled with a fine lens, say EF70-200/2.8) instead of a macro lens?