one thing you'll find DJ is that all zooms are going to have some barrel distortion at the wide end, usually changing to pincushion distortion at the high end. this is more dramatic in the wider angle lenses as well as in the less expensive ones. the quality of the glass cannot completely repeal the laws of physics.
barrel distortion is typically negligible in well made prime (fixed fl) lens - and probably a macro at that.
if you're doing much shooting like in the pistols above, you'll need to invest in a good prime lens, IMO.
