The advantage to the double d type is that you can cut the shafts to length were as the splined shafts have maybe an extra inch on each end to vary the length. On the other hand, I do like the splined shafts because they are a little tighter (less play) than the double d. As far as which brand, I use which ever is the best buy. I,ve never had to use the vibration dampner at all. I'm not sure when that would be needed. If you have that much vibration you probably have a nother problem.

This is just my experience.
Walt