The choice of which shredder is made even more complicated by six security levels and just as many different sizes of cuts.

 Level 2 Stripcut        Level 4 Crosscut

Here's a very simple thought that may not cross your mind as you decide.  The smaller cuts are not only more secure, but they pack down so much better, that you will literally have to empty the shredder less often.

Simple, yes, but something I hope will help you decide.