With a spacing of 2/256, we need a degree-2 polynomial for cos.
With a spacing of 2/1024, we can use a degree-1 polynomial for both sin and cos.

The latter wins:

Run on (48 X 3793 MHz CPU s)
CPU Caches:
  L1 Data 32 KiB (x24)
  L1 Instruction 32 KiB (x24)
  L2 Unified 512 KiB (x24)
  L3 Unified 32768 KiB (x4)
-----------------------------------------------------------------------------------
Benchmark                                         Time             CPU   Iterations
-----------------------------------------------------------------------------------
BM_EvaluateSinTableSpacing<2.0 / 256.0>        2.56 ns         2.55 ns    263530000
BM_EvaluateSinTableSpacing<2.0 / 1024.0>       2.26 ns         2.25 ns    320000000
BM_EvaluateCosTableSpacing<2.0 / 256.0>        2.54 ns         2.57 ns    280000000
BM_EvaluateCosTableSpacing<2.0 / 1024.0>       2.23 ns         2.25 ns    298667000

mockingbirdnest / Principia

A benchmark to decide on the spacing of accurate values table #4006

1760.