I currently own a Tamron 28-75 2.8, along with a 70-200 F 2.8. I am considering selling both and dropping a few hundred on a 24-70L. I currently shoot with a 550D My 28-75 is incredibly soft at 2.8, but sharpens up at F4. Kind of annoying, the build quality is amazingly cheap as well. My 70-200 is a great lens imo, but I rarely use it. I don't shoot too many weddings, mostly portraits, and I am thinking that I can rent a 70-200 when needed, and eventually buy one. I also am going to be purchasing a 5D, whatever the newest version is in a year or two. Would you make the switch or keep the versatility?