if you had to choose between having 2 extra arms right underneath your arms that are fully functional or prehensile tail, which would you choose?

The arms thing with a twist - - I'd want a left-handed arm attached at the wrist (sort of there) of my original left arm and a similar set-up with my right arm so each arm is twice the length of a normal man's arms. Then I'd learn to pitch a baseball with either arm thus becoming the first ambidextrous baseball pitcher in the Majors with the closest release points ever, too.

tail, two arms would become cumbersome a tail is actually useful

My name is Kali

four arms eh? 😳

Tail. Arms are gross. Tail is good balance.

Tail.

Smith and Wesson.

How long and think is the tail and does it bend in all directions? I need to make a fully informed choice here 🤔🤔

That's a tough one. Arms would be so incredibly useful, but a tail ?
A prehensile tail would be both cool AND aesthetic.

Also...an extra set of arms would make wearing a bra impossble. That band around the ribs in a bra is CRUCIAL to its support structure.
Having arms there ?
Nup....i can't see how a bra could be designed to work.