If you want original over 'modern'?, go Sliding.
If you want easy to install over hard, go Panhard.
If you want easy to maintain over more difficult, go Panhard.
If you want really cool to look at over just OK, go Sliding.
If you want less expensive over very expensive, go panhard.
These are just my opinions. You can go just as fast with the Watts/Panhard but the sliding block is so very, very cool.
Jack Beck makes a great set-up:
http://www.orionmotorsports.com/