Well, I haven't left rangefinders altogether--I still shoot my Ms pretty frequently.
However, if I were leaving rangefinders and already had a good 35mm system to use, I would absolutely say the Hasselblad V series.
I have a 500CM (and a 553ELX, and a 500ELX; these two were my studio camera and backup--shooting with both film and a digital back) and several lenses. To me, the Hasselblad is the one medium format system (and I've used and/or still use a Rolleiflex TLR, Mamiya TLRs, Mamiya Press, Fuji GW90 II, Graflex XL) that's as nimble and fun to shoot as 35mm, and nearly as versatile.
Like "pro" 35mm cameras you can get interchangeable viewfinders for the Hasselblad (I use the waist level, the chimney finder, and a prism for various things), you have a variety of lenses from pretty wide to (mostly shortish) telephoto, a variety of focusing screens, extension tubes/diopters/bellows for closeups, there are backs available to shoot Instax, you can shoot film or digital with the same body & lenses, etc., etc. Walking around with a Blad and either an 80mm or 60mm isn't tiring at all and is fairly compact--certainly for medium format. And the lens quality is, like Leica lenses, legendary.
If I ever decided to forgo 35mm altogether, or was told I had to abandon all the other formats I have and had to stick with only one, I'd happily shoot exclusively the Hasselblad V and probably not feel I was missing much by not having another option, in smaller or larger or the same format.