Depending on how much portaging there is (and really, it's more the lengths of the portages, to me), I carry either a full sized 32" bow saw, a 24" wooden take-down bucksaw, or a folding saw. I have 3 of the latter; a Fiskars (it's a pull saw, and I don't like it much, but it's the lightest of the 3), a slightly heavier Bahco Laplander, and a slightly heavier than that Silky Big Boy. They're not much good on anything over about 5" thick. The Silky is the sharpest of the 3, and a dream to use.
I also have a triangular Sven Saw that i don't like very much... just not much depth due to the shape. I'd rather have one of the folders.
Hope that helps.