For me, I'd say it's a four-way tie between the Golgari Swarm, the Gruul Clans, the Cult Of Rakdos, and the Simic Combine.

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Ooooh good question :) To be honest, I'm not well-versed enough in Ravnican lore to give a good answer. I like the Golgari's philosophy of life-death equivalence, but at the same time, I feel like the hive-minded "swarm" aspect is a bit dull. I mean, it works for insects, sure, but the Golgari aren't all mindless bugs. I think.

Gameplay-wise I have always hovered around Golgari and Simic, where my favored colors lie. I like the Simic's crazy adaptability and I enjoy the Golgari's graveyard shenanigans. :)

In terms of Gameplay? I started with the Orzhov Gatecrash starter deck, and the Dimir effect from that block was pretty cool.

In terms of lore? They all jerks. XP

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Yeah, I also love playing Golgari decks. And yeah, I also love Golgari lore. Though to be fair the closest two that are tied for my favorite lore-wise are Golgari and Rakdos. Rakdos specifically because they make me think of a mix of Slaanesh from Warhammer 40k and a circus of murder clowns like the Eldar Harlequins who serve the Laughing God Cegorach.

I've always been a fan of Izzet from when Return to Ravnica dropped, the first Ravnica set I experienced. Before that, I didn't like enemy colours, it was just something that didn't make sense to me at the time. Then RtR happened, and I fell in love with the whole 'mad scientist/sorcerer' thing they have. It's why my favourite Commander deck is Izzet.

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Izzet.

Mechanics-wise, I'm fond of spellslinger-style decks that the Izzet mechanics favor with replicate and jump-start. Lore-wise I'm fond of their pursuit of knowledge, fondness for explosions, and so on. While not often represented in card flavor text, the Izzet are the engineers of Ravnica and are responsible for their buildings, bridges, plumbing, electricity, and so on. They are intimately involved with the structure of Ravnica. The Orzhov pay for it, and the Rakdos provide the labor, but the Izzet design it.

While you didn't ask, I think my least favorite guild is the Boros. They're supposed to be Ravnica's "army" but the purpose of an army is to defend from and attack foreign powers. All of the guilds have some military capacity retained from the pre-Guildpact era of constant warfare. They all already fight each other, so a guild whose sole purpose is to fight the other guilds with a military is pointless. Ravnica has been sealed off from the rest of the multiverse for thousands of years until the events of Timespiral. There are no extra-planar sources of threats that they'd exist to battle and again, all guilds have military assets to do so as seen in War of the Spark once one finally appeared. There are no other countries on Ravnica. They're also not Ravnica's police, as that is the Azorius' job. For all their impressive numbers and armor and structure and so on, the Boros as a guild is the same as every other guild except with nothing to make them distinct in purpose.

All of the guilds are fundamentally flawed, which is I think part of the point. Philosophically, however, I think I like Simic best; while their methods aren't what I'd use, they are literally trying to improve the life (as opposed to improving the standard of living) of Ravnican citizens. I object to the belief that death is a necessity and would be fully in support of hacking life to achieve immortality.

Mechanically, I'm all over the place, as my stable of EDH decks can attest. Think of an archetype, and I've got at least some representation of it somewhere among my decks. I've got at least one deck for every color combinations, with two decks for many, and three decks for a few of the mono-colors.

Of my two-color decks, I think my current favorite is Wort, Boggart Auntie; every creature spell (and some of the noncreature spells) is a goblin, and every single creature token is a goblin. The deck came out much more control-oriented than I'd initially planned, doing things like looping Munitions Expert to keep the board clear of threats.

Of course, enjoying RB Wort makes me think fondly about my Wort, the Raidmother deck, which is built to cast and copy Goblin Game as many times as possible. NOBODY WINS THE GOBLIN GAME! And thinking about how RB Wort came out more control than I planned makes me think about my Rienne deck (which, yes, is not two-color, shush), which came out much more aggro than I intended. Rienne is intended to be my damage redirection "judo" deck, and the only reason I made it as Naya instead of Boros is because of Mirrorwood Treefolk; slap a Lure effect on it, swing, and pay 2WR to have all my opponent's creatures capable of blocking deal combat damage to their controller. No Naya commander really fits the theme, so Rienne is just there to add some recursion for my multicolor creatures (and I added more of those when I finally settled on Rienne). I was intensely pleased when I got to cast Reflect Damage on a Blasphemous Act.