I'm going to break ranks and say the 909 was the far more revolutionary work horse. The 808 has a very 80s hip-hop / electro sound which was limiting. OTOH, the 909 has a very generalized sound with a strong kick and snare that has supported the bulk of EDM for the last 20+ years.
The 808 bass drum dominates UK dance music as an pitched, melodic sound. Distort it through a cheap desk, sample it with a couple of layers and you're away. Drum and bass and dubstep are both built on a foundation of 808s, even if you cant necessarily pick them out.
Here's a video tutorial of some producers walking you through this technique, with a real 808 and an EMU 6400 ultra sampler:
Here's Truly One by Origin Unknown, which uses two 808 samples a semitone apart so that they beat against each other, another of the many many 808 techniques:
Interesting to see the 808 as the foundation of their final kick, but the final result is far from the natural 808 sound. (808 is still a sexy beast tho).
The 909 has been the standard kick for house, techno, et al for a long time with little need for modification.
In the hands of an expert, almost any drum machine can be amazing. For example, I never understood / liked old Alesis drum machines, but wow:
