Originally Posted by Surajit
The telephoto I sometimes might use for wildlife (I know 100-400 L is great but out of budget!) as well as normal travelling around.
You're going to have to decide how much you want to shoot wildlife. The 70-200 f4 is not a good wildlife lens. So, yes, if you want to shoot wildlife you'll be disappointed. But it's a fantastic lens for a 70-200mm lens. Great optics, fast to focus and great build quality - it's a pro grade lens.
The 70-300 is slightly better for wildlife but 300mm is still short. It's smaller than the F4 and has very good IQ for a consumer lens. What I don't like about it is the plastic build (most consumer lenses are plastic) and the fact that the front turns during focusing (as opposed to the f4 which focuses all internally so nothing on the outside moves).
So, bottom line is - if you're doing a lot of widlife you'l be disappointed with either lens (a 400mm 5.6 is probably a better choice). Of the two though the 70-300 will do better for wildlife or anything else you need the 200-300mm range for the f4 will do better if you stay within 200mm.
There is a market for both lenses and they both sell well. It's like trying to choose between a socket wrench and a crescent wrench - both good at what they do and both could do the other's job but both excell in different areas.