Great move OP 
Fuh, the war seems to be over now, lol. Made me feel like watching Transformers again. . .
Anyway besides the weight, and the sharpness, and the price, I guess the f/2.8 IS is the best of em all cause like some of you guys said, eventhough the f/4 is sharper then f/2.8 but the f/2.8 it self is sharp already (unless you have really sharp eyes, then you might end up with f/4).
I will say both lens is not ideal for a daily walk-around lens cause of two things. Its freaking long! It will be hard moving around with this lens with you cause of the length (If Im not mistaken the f/2.8 is slightly longer and much wider (in diameter) compared to the f/4), but both lens look the same at the eyes of normal people, it will sure grab people attention (so its best to have like another photographer or some friends with you when you decide to bring this lens around unless its for some event where you are the photographer).
Anyway again, to the op, good move!
I like to move move it, she likes to move it move it, he likes to move it move it, we like to MOVE IT!! move it!!
Fuh, the war seems to be over now, lol. Made me feel like watching Transformers again. . .
Anyway besides the weight, and the sharpness, and the price, I guess the f/2.8 IS is the best of em all cause like some of you guys said, eventhough the f/4 is sharper then f/2.8 but the f/2.8 it self is sharp already (unless you have really sharp eyes, then you might end up with f/4).
I will say both lens is not ideal for a daily walk-around lens cause of two things. Its freaking long! It will be hard moving around with this lens with you cause of the length (If Im not mistaken the f/2.8 is slightly longer and much wider (in diameter) compared to the f/4), but both lens look the same at the eyes of normal people, it will sure grab people attention (so its best to have like another photographer or some friends with you when you decide to bring this lens around unless its for some event where you are the photographer).
Anyway again, to the op, good move!
I like to move move it, she likes to move it move it, he likes to move it move it, we like to MOVE IT!! move it!!