Ab Slider or Ab Wheel

I'm looking for an ab machine that is inexpensive and easy to use at home. Usually I do my ab exercises in the gym, but I'd like to have one of these lying around when I'm bored...
Has anyone used both or either of these products who can give me some more info about which is better?:
(sorry for the long links, I'm not sure how to make it shorter)
 
Ab Slider (or any similar product):
http://www.amazon.com/gp/product/B000AAQWL6/qid=1143079079/sr=1-1/ref=sr_1_1/102-2460272-2632141?%5Fencoding=UTF8&n=3407741&s=sporting-goods&v=glance
 
Ab Wheel (or any similar product):
http://www.amazon.com/gp/product/B0000AVBAK/ref=pd_sbs_sg_4/102-2460272-2632141?%5Fencoding=UTF8&v=glance&n=3375251
 
Thanks!

The first one, piece of crap. The second one though, is a more ergonomic, more compact piece of crap.
J/K- But not really- Personally, I hate most of these home ab devices. You can really get a much more effective ab workout without all these gimmick machines- Plain old crunches target the abs very nicely, decline crunches even more so, reverse crunches, hanging leg and knee raises- There are plenty of things you can do that are just as effective, if not more so, than any of the as seen on TV stuff. None of them live up to the hype really.

Thanks for the reply.
I feel like I get enough crunches at the gym, and I do them with a fair amount of weight (around 35 lbs.) Since I don't have any freeweights at home, it's kind of tough to get the kind of ab work I want without piling odds and ends on my chest to make up the weight. It's also awkward to leg raises and things like that at home, which is the only place I'm looking to use this thing...
Also, I tried one of these things before and it definitely kicked my butt.
Thanks again!

For the price of the ab slider you could buy some dumbbell discs and use those.

I really like my ab wheel.  Not exactly the same as the first picture but close second.  What do I like about it?  Just variety to the crunches and other ab exercises.

Marc C. David - NGA CPT
Author of NoBull Bodybuilding
www.nobullbodybuilding.com