On the note of looking different I'm so happy your party can change clothing, I wonder if having them in disguises can sneak them through unfriendly areas.
Yeah, I think his hat being gone is a big part of it since he hasn't been seen without it too much.
It's already confirmed the PC can wear disguises to sneak in. I wonder if companions can do the same.
Might be difficult for Siora. She'd have to make sure no skin was showing since I'm assuming natives aren't joining up with other factions. (Or maybe they are, I don't know. Definitely not the religious one)
So far I'm loving all the outfits I've seen. The style of the attire matches my personal taste very well, which is something I can't say for a lot of games. (I loved Bloodborne's clothes, too)
I'm gonna have fun playing dress-up with all the companions. We'll be the best-dressed squad on the island.
Priorities: cure<clothes<Siora
I'm pretty sure it's Vasco in the trailer lip-locked with our PC. Looks quite different without his hat from that angle. Grey looking hair? Did anyone else think so?
So... it's looking like:
Siora - Available to both Male and Female
Kurt - Available to just Female
Aphra - Available to just Male (?)
Vasco - Available to Male (and Female?)
Do we think that's right? Three of these romanceable companions have been confirmed via Steam DB, and the other seems confirmed from one of the trailers.
Who are you planning to romance first?
First play through I'm thinking Kurt, but... depending on how it goes, we'll see. I did not expect Siora to be available for my female PC so, we'll see how that changes things. And Vasco is also looking pretty interesting to me. I hope we'll get more info on him soon. 
Yes, Male PC will get both females and one male while female de Sardet will get both males plus one female (who we now know is Siora)
So either way you'll get three options with a fourth one being unavailable to you.
This worked out really well for me cause I like Siora and the ONLY companion I have zero interest in is also the one I can't romance
I feel bad for the people it didn't work out for though (mainly m/m players that wanted Kurt)
Vasco could turn out to be a really well-done character, which would be the best-case scenario.
In regards to your question, I'm going with Siora for my first playthrough.
If Kurt and/or Vasco interest me then I might try them when I replay, otherwise I might have a Dragon Age problem again where I keep romancing the same character every time I play (this happened with Alistair, Anders, and Cullen XD I never got to see any other romance paths because not ending up with them was emotionally distressing)
Siora first and depending on how it goes I might get Liara syndrome with her and always end up choosing her even when I want to try another one.
@tudorhousewife I'd say this is very likely the correct answer.