Use Standard Lab Values?

I somtmes use spot colors that I convert to CMYK.  I once read somewhere (maybe here) that results are generally better if you place a checkmark beside "Use Standard Lab Values for Spots."  Is that true?  I'm using Color Bridge Plus colors now -- they're Pantones, but they all have CMYK equivalents.  I don't know if I'll mess up the conversions with that setting or not (?).

Thanks, Phyllis