Corvus Belli makes it too hard to pick a faction: there are a lot of good-looking minis! The only faction I really do not like the look of is Combined Army, though I am not too fussed on Yu Jing or ALEPH either.
I like PanOceania, Nomad and Tohaa minis the most, with Ariadna and Haqqislam coming fourth and fifth. With PanOceania and Nomads I tend to like all of the newer sculpts and am less fussed on the older ones. The newer sculpts are predominantly NeoTerra and Corregidor, so that biases me to those two sectorials over the other options, though these both sound like they are relatively dull options on the table (ie Acontecimento and Bakunin seem to have more mechanically-interesting units). I have not had the opportunity to see the Tohaa models up close (no one plays them here), but the photos and concept art give me a general impression. While I really like some models (eg Clipsos and Nikoul), some of the more core Fireteam models (eg Ectros and Sakiel) rub me the wrong way; it is not that I dislike them, they just do not grab me the way a PanOceanian Swiss Guard or Nomad Hellcat does.
By the fluff, Haqqislam is the only faction that really appeals: they are trying to return to a golden age of art and science. That is a background I can get behind. Super-consumerist/super-capitalists trying to maintain the status quo, super-communists seeking to be the dominant power, anarchists/general crazies roaming space and running organised crime, anachronistic Yanks/Russians/Scots/French giving the finger to Earth, and probably-evil alien 'allies' manipulating others into fighting for them. None of those really grab me. Actually, I like the Combined Army fluff more than most, and they are definitely my least-favoured faction! Honestly, this stuck me as a little odd, as I expected to be drawn into the fluff more than I was.
On the table (from what I understand of the rules/my limited experience), PanOceania seems pretty underpowered and dull (+1BS and lots of access to TAGs seems a poor trade off for the worst specialists in the game). I do not really 'get' what Nomads do (outside Tunguska, which looks like it will be a hacker-crazy sectorial when finished). Tohaa Fireteams sound really interesting on the table, but, again, those are the models I am less excited about. Then again, I do not yet know the game well enough to make a meaningful judgement on mechanics. After years of
40K, I still do not know my playstyle there, so I do not expect to have a clue with Infinity yet