Beginner team pick aka Aquilons v Brood Bros

[ggergnayr]

As the title suggests, I don’t know who to pick, or honestly who would be easier to learn the basics with?

[Lathe Biosas]

I picked up a box of Aquilons and they are challenging to a degree because you essentially divide your army into parts when you deploy your forces.

 

But, I really like them as no other Kill Team plays like they do.

[ggergnayr]

Aquilons were the first WH minis I painted, aside from the free infernus marines in the starter set, and I played a game with them when I got the hivestorm box.
I think the drop token mechanic just bounced off my head a bit. I’ll need to reread their rules and try to understand it better. I may have needlessly complicated it. 

[Lathe Biosas]

If you don't mind losing the Servo-Sentry, you can proxy your Aquilons as Kasrkin.

 

And to be honest, they work on the tabletop roughly the same. You just don't have the deployment/movement bonuses and your Kasrkin aren't as workable in melee combat.

[zulu.tango]

Brood Brothers is a much harder team to collect (kill team box, plus brood coven models for full roster) but has the higher end competitively.
Aquillons are a 1-box team (everything you need you get in the box and there are fewer choices to make as far as what you bring to play. 

Gameplay wise I think the Aquillons are more "fun" since they get the drop mechanic, plus the melta(s), plasma, and "sky knife" dude who can charge on drop.
That being said a well played brood brothers team is nasty. They play the missions better than most teams and the crossfire mechanic can shred people. Plus they have a Patriarch if you want to play a distraction-carnifex type game. 

If you're just learning the game Aquillons would be my recommendation between the two. Both can be both fun to play and competitive on the table, but aquillons have fewer moving parts to learn/remember. 

[Mandragola]

The easiest teams to learn with are usually the marines. Fewer operatives' rules to learn and less stuff to move around the board. 

 

Aquilons are a decent team though and not the most compicated. They basically only shoot, so at least you don't have to learn much about melee. The drop stuff is a bit complicated but once you figure it out you have the advantage of not needing to deploy your whole team. I'd probably stick with them for a game or two more if I were you.