Canon 70-300 OR Sigma 150-500mm
I'm guessing that should be 11-16 and 17-85, and if so that would be my choice as the first two are already in the kit. The 70-300 would fill the gap and also provide a light weight duplication of a large part of the 150-500's range for travelling.
The other option limits the range when travelling without gaining much at all, if anything, elsewhere.
Just a quickie on this.....its ironical how PhotoPlus Mag has given the Sigma 18-250 the thumbs up and the winner of its super zoom section....and say its a great travellers lense.
I tested it today and found it incredible soft however that could just be me i suppose. :]
Well, it usually comes down to opinions and what you test against...
Just because a particular lens wins these sort of back to back tests (often it's the Tamron 18-270mm VC) doesn't make it great. In this category, it makes it the best of a bad (or at least heavily compromised) bunch.
They won't compare the Sigma to any 70-300 as they're not comparable lenses. But I'll bet you that at 200mm the 70-300mm is much sharper...
Photography equipment buying is all about compromises, and I guess some people are willing to compromise on image quality and speed in order to gain on being cheap, light weight, and covering every focal length they might need while on holiday. And it's probably okay for many users for holiday snaps, and likely better than a compact/bridge super zoom in most/all respects.