They are definitively more laid back than Caiques.
Caiques are more like Loris where energy and having to move constantly are concerned.
Trust me, no Poicephalus really can compare to them in that regards, they are much calmer. Active, but no where near as active.
As with biting, every caique owner I've talk to in person, and there were a few, were worried about an unexpected nip on a stranger. Not every senegal owner I've met (and any other Poi) had the same concern.
Edit: I also believe that Sennies bites are more predictable. There might be just a little warning, but you know it's coming (although maybe too late). Not always the case with Caiques I was told. One of the owners I've met would let their Meyer's and Hawkhead go to anyone. Their Caique? No. And they would warn anyone wanting to approach it that the likeliness of them getting bit was almost guaranteed. It did jump on my SO and took a chomp out of him before returning to his perch.
Anyways, I did mention it wasn't the nippiness as much as the extra energy they have that would stop me from getting one.