BA vs BSc at KCL (due to Semester Abroad)

Hi everyone.

I'm a second year student at KCL, doing a BA/BSc in PPE. I recently got offered a semester abroad at a UC campus (I'm assigned at the discretion of UC, I can rank 3 of them but it's not guaranteed, I'm ranking Berkeley, LA and Davis as my 3) which will cause issues for me due to my Econometrics requirement. UC generally does not allow for reciprocity students to undertake Econometrics modules, which would force me onto a BA track. 

I have 3 main questions:

1. Would doing a BA be very different in recruitment from doing a BSc due to the "STEM" preference in certain spaces?
2. Would doing the BA, with something like UC Berkeley on my resume offset it?
3. Would it be safer to just do my BSc and go abroad for my masters if I could?

I know that in the UK and EU, masters don't really play a large part in recruitment, since undergrads are normally targeted. Regarding the STEM thing, I was told probably 2 years ago that STEM degrees are worth more to recruiters than BA degrees (from this very forum actually, but I've since lost access to that account).

I'm looking to work in S&T, Fixed Income or Forex Desks, since that is where my interest mainly lies.

Thank you for your time.