Sad that this is only 4.5*. Should be 5*+ in my opinion, not only from a personal taste, but instead this is a largely preferred ratio by many people just like the 5:1. The right amount of vermouth to the gin and the best balance with a lot of rounding the vermouth does. It's like the gin's botanicals are wrapped by a blanket of softness and subtle sweetness of the vermouth's winey character and botanicals. I split my vermouth between a citrusy vermouth and a more classic one (Dolin) with a 45%+ ABV gin (recommended for best results, in my case Finbury 47, an absolute bargain).
I like this ratio, but prefer half of the Vermouth to be extra dry, and the other half sweet. I find this gives a depth of flavour, especially when shaken.
I say go for the 1:1 or 2:1.5 ratio. You may be surprised. I usually prefer a 5:1 Martini but those recipes somehow come out better balanced than the 2:1 ratio.