RX100 - ND4 or ND8 ?

If I purchase just one ND filter, which one I should choose.
ND4 or ND8 ?
For DSLR, ND4 should do the job, but RX100's minimum aperture is
only F11, while for DSLR it goes up to F32.
So, should I get ND8 ?

Any other tips, recommendations, and suggestions
regarding ND filter for RX100 would be appreciated.
(BTW, has anyone used ND400 with RX100? If so, is it effective?)

Thanks.

--
cj