Subwoofer Footing - Connect or Isolate?

I discovered early on that placing my Velodyne HGS-15s of Auralex SubDudes really improves their performance.  I do enjoy that subtle more felt than heard experience when a large pipe is played by the organist.

I just bought 4 Townshend Seismic pods for my 140 pound sub. I say vibration isolate your sub from the floor.

Using the pods is a relatively inexpensive way to completely isolate your sub.

I use Auralex Subdude platforms. Things sound more defined, controlled and right with them. 

You can not isolate a subwoofer from a "springy" floor. It will shake/resonate from the bass regardless. The solution to a "springy" floor is to fix the floor which can be easily done with lally columns and a header. Once the resonance frequency of the floor is above the subwoofers highest frequency you are in business. 
People imagine all these EVIL gremlins lurking around corners. Lay instinct run amok. 
Any shaking, movement or vibration in any loudspeaker is distortion. With subs this is viciously true. The failing of most subwoofers is the enclosure. It is extremely hard to contain that vibrating monster in a cost effective manner.

SVS sells their SoundPath sub isolation footers for only $50 and offers a generous risk-free trial so you can try’em at home. They are said to both improve bass and reduce transmission and get excellent reviews from customers who bought them. No brainer in my book. Best of luck.