They're not quite offering the same thing though.
Just in principle I know the approaches have their differences. Fundamentally they're both opening their 'stores'/markets to more content from indie developers. Yes, MS's is more accessible, the vetting process isn't as rigorous. From a developer point of view that may be preferable, or not, maybe a developer would prefer not to be a small fish in a big pond, for example.
As a consumer, though, it remains IMO that we'll have to wait for these 'stores' to open before we can really get an idea of which might be preferable to us individually.
I think though I personally like the XNA approach of as few barriers as possible, I like the sound of that at least.
I will put bets on the being one when its released
When Home's released? That's pretty soon, I'm not sure if I'd expect a nicely packaged SDK to be released initially too. When they last spoke about the possibility, it sounded like something they were considering, but that wasn't an immediate priority. I dunno, maybe they put more people to work on that latterly, it would be nice if they did.