pito:
.. a clock2clock comparision says teensy shall be ~3times faster than Uno (@16MHz) and teensy is 32bit CM3, so a 32bit fp sin() cannot be "only" 1.6x faster than Uno.. saving to an array cannot create such overhead, indeed..
My 2 cents: A possible explanation may be that the compile options for teensy are not similar to those of UNO.
Best regards
Jantje