Upload & Sell: On
The definition of "better" depends on your particular criteria. Also, I haven't directly compared the two, so I can't say anything other than that Leica tends not to replace an optical design unless they've come out with something that is superior either optically or ergonomically. I like my 2nd generation Summicron 50, but it is only slightly superior to most--and only slighter inferior to some--other 50mm lenses. I have a particular fondness for its glow around near-focus subjects combined with its lack of color fringing in bokeh, though.
For portraiture, whether to go with 35 or 50 (or ~85 or even ~150) is more a matter of style and approach than the optics themselves. From what I've seen, a 90/2.8 will surpass a 50/2, which in turn will surpass a 35/2, in terms of high contrast and high resolution acutance. Of course, images from a 90mm will look quite different than images from a 35mm due to framing and perspective. Probably the smoothest all-around Leica that's still affordable is the Macro-Elmarit-R 60mm, which might be ideal if you're looking to do both subject isolation portraits and also subject-in-environment portraits with the same lens.
You see, the problem is that one can end up wanting every single Leica R lens. So, be careful.