Last year's 50 point defensemen include
Karlsson
Burns
Schultz
Hedman
Shattenkirk
Keith
Byfuglien
Krug
Hamilton
The wingers who scored 30 last year but not 40 include
Marchand
Skinner
Pacioretty
Lee
Forsberg
Arvidsson
Panarin
Tarasenko
Laine
Atkinson
Pastarnak
Kane
Oshie
Simmonds
Eaves
(I didn't include Ovechkin because I think calling him a "30-goal scorer" is disingenuous to his career resume)
If I had to choose blind, I take the defenseman, and I take the defenseman in most cases. If we're talking about the traditional 30-25 winger, like Atkinson, Lee, Simmonds, etc., I take the D.
But I would definitely take Panarin, Marchand, Tarasenko, and Kane over a handful of those defensemen. So it depends on the two players and how strict the "30-goal" definition is. Is it the traditional 30-25 power forward, or an elite all-around winger who happened to score 30 goals?
EDIT:
@Morgs Had it first, nicely done bud.