How can I determine if either of these tenoning jigs are worth the asking price?

What should I look for when inspecting them?

http://rochester.craigslist.org/tls/5974106281.html

http://rochester.craigslist.org/tls/5934397957.html

Woodcraft has one on clearance for $60 but the reviews are terrible.

https://www.woodcraft.com/products/w...r-tenoning-jig

Just in case it matters, I do not have a T-slot on my table saw, just the standard U.

As always, thanks for any advice/recommendations.