Flash Sync Speed (1/200 vs. 1/500)

While waiting for my new D3100 to arrive, I am thinking about what I will lose going from D40. Other than the convenient file size (sweet 6MB NEFs) and the remote, there is the flash sync speed.

But am I right to think the effect of flash sync speed should be pretty close because the base ISO for D3100 is 100 vs. 200 on D40?

e.g., a beach scene you want to shoot with fill flash may meter at

D40 = 1/500, f/11, ISO 200
which is very close to
D3100 = 1/200, f/11, ISO 100 (that D3100 may calculate)

It would be equal if the D3100 had the sync speed of 1/250. So that's about 1/50 difference, which would not result in much different required aperture. Or am I completely missing the point of high flash sync speed?

Please enlighten me.