NI has released a great tool for comparing data acquisition products, which you cand find at http://sine.ni.com/gc/app/ui/page?productCategory=7863
You select the parameter you'd like to compare for the X and Y axis, and the site draws you a comparison of all NI data acquisition products against those two axes:

After making the graph, you can zoom in, click on specific products, and link to the product pages.
Try it out, let me know what you think!