What did you find inadequate about your kit lens?
I find the 24-105 to be more useful for outdoors than the range of 24-70. I don't have that lens, but I did own a Tamron 28-75 f/2.8. I do miss the larger aperture though, but for me I prefer the reach. IS is also nice to have. Finally the 24-105 is smaller and lighter than the 24-70.
Rent one or both and give them a try.