Optimizing for FNC and TB scores

Hi @mdo and @jrb, I have a question about calculating exposure.

Earlier in this thread @mdo uses this:

And in a different thread (Model Diagnostics: Feature Exposure) @jrb used something a little different:

Both go up as exposure goes up, and both stop at zero if exposure is zero. But to me, @jrb’s version has the nice additional quality of being bound to lie between 0-1.0 no matter how many features are being considered.

Are there other reasons you might choose one over the other? Such as accuracy, or speed, or … ?

Thanks,

prc