I am thinking on buying the Tokina 11-16 f/2.8, Don't you guys think it's the best wide angle lens out there??... also, I'm looking for a zoom lens with a constant f/stop, but I don't know which would be the best lens to buy, the options are, the canon 17-55 f/2.8 ($1180) or the canon 24mm-70mm 2.8 L series, but it costs around 1400... the first choice has a EF-S mount, but I don't think I'm going to buy a Full Frame Sensor for a long time, so should I pay around 200 bucks more for an L series lens, Will it make a lot of difference using an L series?... or what exactly are the differences on these red ring lenses?...