The call to a guild at the prerelease is going to be tricky. On the face of it, all 5 guilds have things going for them at this early stage:
Orzhov - extort is a
fantastic limited mechanic. Whenever you play a spell, you can get a cardless 2 point life swing. Most players would be fine with investing 20 mana over the course of a limited game to, you know,
win the game, and putting you further out of reach is certainly relevant.
Boros - typically fast colors, and batallion is a very aggressive ability. Likely to be one of the faster guilds next weekend. Throw in that both colors are colors of removal, and there's a recipe for success.
Gruul - the other aggressive deck for next weekend, but
bloodrush is going to be brutal. It's a very good aggressive mechanic, both in limited, and some of it will see play in constructed. I mean, look at Slaughterhorn - you can either play it as an
almost Giant Growth 
, or as a 3/2 for 3. That is, you can either pump or play an on curve creature. That kind of flexibility makes for stronger decks. The issue with Gruul is going to be that the more bloodrush you use to get damage through, the more card disadvantage you're giving yourself - which often hurts late game - and if you use bloodrush as pseudo-removal while attacking into a block, you're also opening yourself up to a 2-for-1. That is, bloodrush is double edged, for sure.
Dimir - a controlling set of colors, but cipher is probably, IMO, the best ability in limited from the 5 guilds. It's usually going to lead to card advantage and is quite straightforward to use. Just hope that you don't get much mill. That 4 mana "flying token + cipher" uncommon should prove very good.
Simic - I'm probably going to go Simic... not really because it's the best choice (if white and black get enough decent removal I'd imagine Orzhov would be for extort), but because I love UG. Evolve is also a great mechanic, making your drops stay relevant for longer than they would in other limited environment. It's also likely to be the guild with the least access to removal in limited. Actually, maybe I will go Orzhov... staying true to my
is all well and good, but I do like to win, and it feels like Simic's going to require a higher quality pool of cards to do that with than other guilds would.
Very, very tough choice... I'll wait til I see all the commons and uncommons, and probably do some 5-pack sealed deck generations to see what kind of spread comes up in the other 5 packs, but yeah, at this stage Orzhov is looking very nice to me.
