i have tried lots of goofy ab machines in my day. of course this is just my opinion but an ab wheel has always worked well for me. on the down side i usually get bored with them. if your abs are strong already an ab wheel should be relatively easy to use however when i first tried an ab wheel it kicked my butt. the "ab slide" is kind of an introductory version of the ab wheel because the motors help you out but if your not a beginner in the abs department i really dont recomend that one. its kind of expensive and after a month you will probably not get much use out of it anymore.
