Just the Sonicaire. I do not usually use the Waterpik for my teeth, as brushing them gets them cleaner. I use the Waterpik for ears only :).
If one had braces, I could see how the Waterpik would be invaluable for tooth/brace cleaning, however I can massage my gums (Which is all I would need it for) just fine without it.
A few weeks after starting to use the Sonicaire (I brush a couple of times per day), suddenly my teeth became very sensitive, gums swelled up and began to bleed, it seemed like my teeth felt like they were going to explode, and the muscles in my jaw constricted so that it became too painful to open my mouth to eat.
As a matter of fact, that happened just before it all hit the fan with my health, and (it has now been 2 years). Although there have been other events which I know have contributed to the physical challenges, there was enough synchronicity with the advent of the Sonicaire to prevent me from using it again.
As a result, I keep the Sonicaire on the side of the sink, where it shall remain until my rings need cleaning.