i am wanting to upgrade my kit lens but I am having a hard time deciding. I have a crop sensor canon now but I'm not sure I want a crop sensor lens in case I upgrade to full frame. I shoot landscape and portrait. I am looking at the 17-40 l, the sigma 17-50 and the 17-70. But I'm open to any ideas. There are just so many lenses it's hard to keep up w it all. Thanks.