Magnification 7X, 8X, 10X, or 12X compact
Compact binoculars are harder to steady and use than full size binoculars, so if this is your first compact, I strongly recommend keeping the magnification down. 8x is a good choice, both in terms of magnification and selection. Read my article, [url=Buy Compact Binoculars]Buy Compact Binoculars[/url] for more on the pros and cons of compact binoculars. You do give up some things in a compact to get that great portability.
Price is still the best indicator of quality, not brand and all those brands mentioned make the majority, if not all of their binoculars in China, anyway. Only exception is the excellent Bushnell Elite 7x26, which is still made in Japan. The best bang for the buck in optics in a compact is a reverse porro compact, such as the [url=Buy Compact Binoculars]Nikon Prostaff 8x25[/url], the Pentax UCF X II 8x25 or the Vortex Vanquish 8x26. This style won't be as trim and portable as a roof prism compact, but it takes a more expensive roof to stay up with them on the optics.
In a roof, try the Pentax DCF SW 8x25 or the Leupold Olympic 8x25
Although there is no official dividing point between compact binoculars and "mid-size" binoculars, most folks generally agree that you are moving out of compacts when you get to a thirty or thirty two mm objective, i.e. and 8x30 or 8x32. This size definitely gets you more performance and better ease of use than compacts, but with some size and weight advantages over full size binoculars with 40 or 42 mm objectives. In fact, I have used an 8x32 as my "full-size" birding glass for many years.
Going to an 8x32 greatly reduces options for a porro prism binocular, so you'll be looking mostly at roofs. The Brunton Eterna 8x32 is a good value and the old, non HD version of the Bushnell Legend 8x32 may be the best value going in an 8x32. Or you might want to step up into something like the Vortex Viper 8x32 although I would hesitate leaving a more expensive bino in a vehicle on a full time basis.
In terms of features and the portability you want, the Bushnell Trophy XLT 8x32 and the Vortex Crossfire 8x32 are great values in a roof prism.