As Evernote and ShoveBox serve different purposes, which app is best for you depends on what you need it for.
Evernote (and DevonThink, Together, Yojimbo, EagleFiler, and whatnot) are appliations which help you organize your stuff in the long term. Files dropped into one of those applications are meant to remain there forever. Fancy search technology such as tagging or advanced information retrieval methods eases the pain of retrieving them later.
ShoveBox, on the other hand, is a temporary bucket for things that you don't want to deal with right now because it would interrupt your workflow - a web page or an image that you stumble upon while surfing the web or a spontaneous idea that springs to your mind while you are doing something else. If you use ShoveBox correctly, its inbox will be empty by the end of the day or week.
I for one found that ShoveBox is the thing that I need. Had I wanted an app for long term filing, I would have gone with Together because, unlike its competitors, it doesn't move my files to its own database (it only manages refernces to my original files).
A more detailed explanation of the difference between the two kinds of applications can be found
in a blog post by one of the creators of ShoveBox.
