Just chippin' in. The 1:1:1 ratio is a modern myth. It is indeed the recommended ration but it is equivalent of tendering the vines and vinify the grapes always in the same way regardless of the vintage. It is an aspiration for those who wants to show the true value of the soil but; let's face it, it never happens.
Depending when you drink AND your bitter/vermouth, you may want to adapt a little the recipe. I am not calling for a 2:1:1 or 4:2:1 ratios but most bar tenders skew the ratio towards gin and vermouth (in this order) and away from bitter. By most bartenders, I mean mixologists around London yet again it depends on the ingredients and time of day. Before dinner you may want to tone down the gin and have more vermouth (unless it is Antica Formula whose vanilla I find overpowering) and in the summer, maybe, add more bitter (tempered by some orange bitters angostura?). In my experience, aromatics of delicate gins (i.e. lightly flavoured vodkas) are lost in a Negroni whatever ratio you use.
Just my 2c.