I'm new to this forum and wanted to get people's recommendation on which lens I should pick up. I'm currently shooting a 40D and only have one lens at the moment, 24-70 f/2.8L, which I love very much. I'm planning on upgrading to a FF body at some point and would like to have a good set of standard tele zoom lenses that covers the most commonly used focal lengths. Right now I can't decide which lens to buy, between the 16-35 f/2.8L and 70-200 f/4L IS. I know that they are completely on two different ends of the spectrum, but I'm trying to figure out which one will get more use.
Argument for 16-35 f/2.8L is that I simply need a wider perspective. I like landscape photography, but I actually want an ultra-wide angle for tight shots and indoor use where I don't have a lot of room to work with. Problem is, I have a 24-70 on a crop body. Will I notice much difference between 16-24mm? I considered the 10-20mm EF-S, but it's $700(half the price of 16-35) and is not compatible with FF cameras. I haven't considered the Sigma or Tokina alternative.
Argument for 70-200 f/4L IS - It's arguably Canon's best telephoto zoom lens in the 70-200 lineup for IQ. Compared to the its 2.8 brother, it is lighter, smaller in length and diameter, equal in effective aperture because of its 4 stop IS, and cheaper. 70-200 is a very useful range for just about everything including portraits. It also compliments my 24-70 since there is no overlap in focal length like the 16-35. It is also cheaper than the 16-35 by $400. I don't really need the 2.8 for what I shoot and not interested carrying something so big and heavy as a walk-around lens.
What to do? I'm no pro and don't like to carry too much gear on me when I travel. I like to keep it light but don't want to miss a great shot because I don't have the right focal length.
I need to make this decission rather quickly because in 2 weeks I will be traveling to Greece (Athens incl. the islands, especially Santorini) and Prague. I will be taking lots of outdoor shots and also indoors like churches, castles, and houses. I really should buy both, but I'm planning on packing light and want to minimize on my choice of lenses.