Here are some of the major differences, IMHO. Attract can run on many different platforms (Windows, OS X and Linux -x86, x64, Raspberry Pi, Odroid) whereas hyperspin can not.
Attract is easier to configure, faster and more stable. And, problems actually get fixed. Unlike, hyperspin, where it can take a long time to get simple fixes done, if ever. How, long did it take to just get the joystick controls to work in hypersin?
Attract can import themes from various frontends (Hyperspin, MaLa, MameWah). Though, hyperspin themes are still a (WIP).
You can code your layouts to scale up to 1080p, hyperspin can only do 1024x768, unless that has changed.
Filtering and sorting is far superior to what hyperspin can do. You can get very granular by using filtering rules. Hyperspin, actually needs rocketlauncher to be more functional.
Where hyperspin excels is with its thriving art community. There are some talented theme creators over there, for sure. But, we have some here too, it's just more involved and requires getting your hands a little dirty with some code. Attract has no theme editor like hyperspin does. But, of course for hyperspin themes, you can still use its theme editor.
If you take the time to read the layout and readme files, you can create your own themes in no time or you can just use some of themes that have already been created by other members.
Oh, btw, there is en excellent step by step tutorial on how to configure attract by akafox in the forums. See
http://forum.attractmode.org/index.php?topic=344.0
