In Vuo, the method is always a linear formula ((1-C)*(1-K)). This is the same one used by http://rgb.to/hex/44ff30, for example.
A different site, http://www.codecrete.net/CMYK, which uses the ISO Coated v2 300% Color Profile, gives a result closer to what you're seeing in Photoshop.
If you're interested in Vuo supporting more than one color profile, you're welcome to create a feature request.
Thanks for the explanation Jaymie.
Yes, with my little understanding of the color world, it seems CMYK mainly exist because of the printing methods.
So by default I would have rather preferred a generic CMYK color profile rather then a (1-C)*(1-K) method.
Because even if it would not have covered all the subtle printing results, it would still have matched a printing result more then (1-C)*(1-K).
I see very small use of CMYK use for a RGB like gamut.
But perhaps I'm very wrong, and a wide range CMYK gamut is useful for Pantone conversions / matchings.
Perhaps a small addition to the node without a Feature Request could be an option for either (1-C)*(1-K) or Generic Printing CMYK, and a Feature Request for a larger profiles options.