I'm an upland bird hunter, who always carries binoculars. I'll say, that you don't want cheap optics. They'll make your eyes hurt, through eye-strain, and not reveal animals to you (that you ought to have seen).
In a bright environment, I carry compact REI house brand 7x25's, covered in nylon cammo tape. I'm not sure how well they would work in a dark and gloomy forest, or just how water proof they are.
If where you will be watching is bright, you can possibly go with the smaller objective lenses. But darker places call for bigger objectives, to gather more light. It is very instructive to glass stuff at twilight. Optics with good light transmission, will take dark gloomy stuff with fuzzy details in it(according to your unaided eyes) and "light" it up, giving you a bright image, full of clear details.
I went for the compacts because of portability and handiness issues. Had they been as large as 7x35's or 7x50's, I'd prolly never take them. But since they are so small, they get taken a lot. I'm very happy with improved chances to see animals, that carrying handy optics makes possible.
P.S. I don't buy optics sight-unseen. Walk into some big optical store, try a few pieces out, and buy the particular one that has the best image. You are looking for:
-Crisp, edge-to-edge view. Once you focus it, there should be no fuzziness.
-Straight lines should appear straight.
-No colored "edges" around objects (I think this is called "spherical aberration")
-No double-images.
-Easy to re-focus on stuff at different ranges.
-Should state "fully multi-coated" lenses.
Do look through some crappy, cheap stuff first, so that you are freshly familiar with what a bad view looks like.