The golden rule with Infinity is go with what you like the look of. Aesthetics are more important because you can play the army however you want.
...almost. Ariadna is a slightly different kettle of fish. They don't have the high technology levels of the other factions and that means you can't have any hackers. Apart from that you can play them pretty much however you want. Low tech means no TAGs but you can still run elite lists. You have slightly more options for running larger lists of cheap units with this faction. Other factions can do that too but generally more restricted. You still have access to cool snipers, camouflage, infiltrators, etc so you can still play lots of different ways.
On to Haqq... These guys have a couple of interesting edges too which can be exploited. You still have all your standard options though so play them however you want. What they do have access to is an abundance of high skilled medics, this means you can potentially save your models from bleeding out on the field of battle and even get them back to the fight. Your enemy can still make a point of killing them off before you can save then but this will cost them orders and that is veruy beneficial to you. Haqq also have some awesome assassins to play with which puts camo, infiltration, deception and brutality at your disposal.
Overall, I still say go with what you think looks coolest. The rules for Infinity are going to be the thing that keeps you wanting more whatever army you play. Just make sure you love the miniatures. Once you get into it more you can even look at picking up a second army so you have both! Or be like Skyfury and buy EVERYTHING.

Eventually you can even look into Sectorials for more specific play styles that you are gravitating towards. Maybe you find out you like charging the enemy with a host of Galwegians, Wulvers and Dog Warriors. Then you can check out the Caledonians. Or maybe the Hassassins are your calling, so check out Hassassins Bahram.
Most importantly, at this early stage, buy a starter box for a non sectorial and get a feel for them. Proxy anything you want to and buy what looks prettiest. The guys around here will steer you right on army building if you need help but although you can make a bad list most lists will be just as effective as anything your opponent can field. The beauty is that no one has an edge or is
OP.
I hope that helps.