The TS-E 90mm + 2x Canon TC (=180mm), the EF 100mm + 2x Sigma TC (= 200mm), and the Sigma 150mm + 1.4x Sigma TC (=210mm) tested at different apertures, same subject, tripod, mirror lock-up, and the 580 Canon flash.
Exif data may not be correctly adjusted for TCs.
Weights: 180mm: 865g, 200mm: 900g, 210mm: 1165g.
The 210 will AF at non-macro distances, but the other combos are completely manual.
The 180mm isn't a proper macro-lens, but gets pretty close. A 60mm wide object fills the full frame (36mm).
All shots are at the 90mm's minimum focusing distance.