Matt, welcome to the forums!


Your dilemma is a tough one for sure! I'll give you my opinion though.


I have a 20D (so we're dealing with the same crop factor), aTamron 17-50 f/2.8, a 50 f/1.8, and a 70-200 f/4L non IS.


In my experiences, the perfect walk around lens for me would be a mix between the Tamron and the 70-200, possibly ohhh, a 24-105.


But it really depends on if changing lenses is a problem for you. In my opinion, you'd certainly benefit more from the 70-200, however, you'd have to change between lenses and you would lack anything wider than 50mm (or around 85mm with the 1.6 crop). That's not very wide at all. I find that I use my Tamron's range quite a bit.


So I guess to me, it looks like it's either semi-wide and convenience in the 24-105, or more focal length and a great telephoto zoom in the 70-200.


Hope I helped a little bit!


Rodger