Nothing about Sing Street appeals to me (based on several viewings of the trailer), so I haven't seen it. (I was in my 20s during the '80s, so the kids are too young for me to relate to; also I don't like much of what passes for "'80s Music.")
I would argue that Everybody Wants Some!!! has one big foot in the '70s (it takes place in 1980, right?): everything about it seemed '70sish to me. Also, unlike Sing Street, the kids in Want Some!!! were my peers (other than their being gorgeous and athletic); that one really resonated with me.
Anyway, since I've only seen one of the films, I'm not going to vote. But I'll be damned if I let an opportunity to pump up my post count go by, especially after losing a bunch in the recent deletions. OH THE HUMANITY.