I chose the sigma 8-16 when i was searching for a uwa lens. Sometimes i wish i had gone for the tokina for the faster 2.8 apperture but when i tested the 8-16 i was sold on how much coverage i had at 8mm. Altho it cant accept filters and is a slower lens i prefer to tripod mount my camera for wide angle landscapes. If i need speed i just crank up the iso a lil bit and compensate. Theyre are both good lens.