If you find 250mm too short for wildlife, increasing to just 300mm will not make a difference as 300mm also is too short for 'wildlife'. The simplicity of one superzoom delivers only simplicity, not image quality. If wildlife is an interest, consider a lens specific to this need, not a do-it-all lens that fails for wildlife. Your best bet is the EF 100-400L II, although this lens is large and heavy and expensive. With your 80D, you can extend for an effective 560mm. If still interested in a more modestly priced superzoom, look instead at the Tamron 18-400.