The Canon 100-400mm V2, and the Nikon 80-400 V2 both have extremely fast AF. Combined with their capable bodies and top notch optics, they made formidable outdoor sports lenses. The question is whether the Pentax combination will match it in Optical AND AF speed. They are certainly asking top dollar. When you pitch your product price-wise against the big boys then you'd better be at least as good.
The problem for the Pentax 150-450 / full frame combination is not only competition from the Canon/Nikon FF's, it's from their own amazingly capable DA*60-250. The 60-250 is astonishingly sharp, it's possibly the best zoom lens ever made by Pentax. I have a K-5c and DA*60-250, so to get an improvement from this combination I would have to go FF and spend over $5,000 AUD (Pentax FF body plus the 150-450), which is not something I'm prepared to do, not this week anyway
Last edited by twitch; 02-11-2015 at 03:22 PM.