Macro lens comparison 50mm, 100mm, 180mm

Canon 100mm Macro USM vs Tamron 90mm Macro

Sigma MACRO 50mm F2.8 EX DG $249
Canon EF-S 60mm f/2.8 Macro USM Review $380

Canon EF 100mm f/2.8 Macro USM $469
Tamron SP AF90MM F/2.8 Di $429
Tokina AT-X 100 PRO D 100mm f/2.8 $411
Sigma MACRO 105mm F2.8 EX DG $358