Which accuracy should I set? (Spectre Simulation)

[Vincent]

I'm simulating a Sampling and Hold circuit, which has 14 bit
resolution. The simulator is spectre. When I set ‘accuracy
(errpreset)' to ‘moderate', the result (after DFT of transient
simulation results) shows about 12 bit resolution. However, after
setting ‘conservative', it has about 14 bit performance. My question
is, which result is more reliable?

Also, with switched capacitor circuit, like this S/H, which integer
method is better? Trap, Trapgear2 or Gear2?

Thanks a lot.