What ever you do don't compare the 24-105 to the 24-70ii. If you do you will be walking out very poor. The 24-105 is a great travel lens. Light, great range and IS so you don't necessarily need a tripod often. Although I'd say if you already have a 16-35 and a 50mm I'd skip the normal range zooms entirely and just pick up one of the many excellent versions of the 70-200 made by canon. You honestly wont miss the 35-70 range its rather boring imho. Personally I was turned off by the weight, size, and price of the f2.8 versions of that lens and ended up with a great copy of a 70-200 f4 IS. If your heart is set on a 24-70 zoom don't forget to look at the tamron. You get 95% of the performance at 50% the cost to the new canon.