To make it short, which lens would you buy in this situation, and why? I'm trying to figure out in my mind how to "prioritize" criteria in lens buying. All prices in Canadian dollars. Lenses are Canon mounts. Sigma 70-200mm f2.8 APO EX DG MACRO - $800(used) Canon 70-200 F4 (I'm assuming L) - $600(used) Canon EF 70-300mm F/4-5.6 IS USM - $840 new Canon EF 75-300mm F/4-5.6 III USM - $250 new assuming that the extra zoom isn't a huge issue.