I think you need to take a look at exactly where the roots of both spots come from. Now I am no expert on Buzz, but it seems to me the music there is more grounded into techno, d-n-b, and very progresive house.
I personally don't think that those are fields where a lot of "artists" come in and perform. (i.e. singers and such) Those genres are dominated and produced by people who are mostly DJ/producers. And I do think they do a good job of bringing in international talent. But it just doesn't lend itself to being something more than just a DJ spinning. Now the other place, I can totally give an expert opinion on. The type of music that can be found at twilo is predominately soulful, garage, disco house which, because of it nature, has "artists" who are the main focal point of the music. Yes, of course you have the dj/producers who create the tracks but the vocal stimuli is provided by the "artist". These 'Respect is burning' nights at Twilo were predicated by the nights at the Soundfactory Bar in the village of NYC (90-94).
Those nights were promoted by Barbara Tuckker (artist) and Lil Louie Vega (dj/producer). Their collaboratory name was The Underground Network. Every wed. nite they brought in three hot acts from that time period and from the past. It was like going to a club to get your dance on and going to a concert at the same time. It is still the best clubbing experience I have had to date. After 94 they moved the spot to Twilo and have been evolving ever since. These events were attended by the same heads that you see at the Shelter. That's just to kind of explain the vibe that was going on. This is not to say that Buzz cannot crate the same type of event (not party). But you have to look at who their style of music caters to. (the techno heads) One is not better than the other it's just your preference. If you want to see that internationally known producer of techy house then Buzz is your spot. If you are looking to check out that artist with the amazing voice along with that bad ass dj/producer who just happens to be spinning that nite, then Twilo, Shelter, and B&S are your spots. These are just my opinions. I'm peace