Hi,
I was hoping for some insight and your vote!
I am embarking on a road trip starting from Bay Area, CA up the Oregon Coast, to Seattle, over to Montana, drive through Yellow Stone, to Salt Lake City, across Nevada, then finally home.
I hope you were able to follow that 
My equipment 5D 2, 30D, Canon 24-70 2.8L, Canon 10-22, 50 1.4.
Intended subject matter:
1) Candid photography
2) Nature (Landscape)
I want to borrow a 100-400 or 135 + 1.4 extender.
Which one do you think I should rent or am I going completely overboard and should just stick with my current selection.
Thanks!
100-400
