My experience as a newer player could be quantified more like this.
If I play man-to-man and average Inept (High) perimeter, when I play 3-2, it is around Mediocre (medium) and 1-3-1 is Mediocre(high). Roughly comparable, 3-2 is a 15-20% increase and 1-3-1 is a 20-25% increase. The inverse applies to the ratings for inside and defense though.
So, as stated above, do your scouting, figure out how your inside players matchup to his.
Also, in a 1-3-1 defense, the 4 position plays at the top of the key, so his Outside Defense score contributes some to the team ratings, while in 3-2, it does not. Depending on your need to shut down the opponent's outside game, you can play the defense that best fits your PF player.
Granted, I play in Div IV and my competition's not comparable to the talent on my team, but I am willing to give one player of the opponents an easier time scoring while shutting down 2 or 3 of his other players. That is a trade-off I am willing to make.