Max Pacioretty and Nikita Kucherov led the league last year with +38. Here are their BY FP numbers with and without the stat:
Pacioretty with +/- = 190 pts, 2.38 FP/G
Pacioretty w/o +/- = 181 pts, 2.26 FP/G
The change would decrease Pacioretty's production by 0.12 FP/G (5% decrease)
Kucherov with +/- = 150 pts, 1.83 FP/G
Kucherov w/o +/- = 140 pts, 1.71 FP/G
The change would decrease Kucherov's production by 0.12 FP/G (7% decrease)
At the other end of the spectrum, Nail Yakupov posted a league worst -35.
Yakupov with +/- = 90 pts, 1.11 FP/G
Yakupov w/o +/- = 98 pts, 1.21 FP/G
The change would increase Yakupov's production by 0.10 FP/G (9% increase)
As the best and worst in this category these players would be affected most. Every player in between is affected less and less. Given that about 90% of the players in BY would see about 2% change or less (guesstimate), I would say this is a reasonable change.
So, my opinion is - get rid of +/-.
I'm still new here and I'm getting used to the scoring. I really won't have a strong opinion on the stat discussion until the season starts and I start seeing stats pour in. I will say, as a first impression, it seems like the best players don't stand far enough apart from the mediocre players in this league. Just doing some quick math...
Players ranking between 51-60 in FP are scoring about 75% of the points that players ranked between 1-10. The top 10 skaters (D included) earn about $6.39/yr on average while the 51-60 ranked skaters make about $2.25/yr on average. So, to sign a top 10 player you're going to pay almost 300% more to gain 25% additional stat production. I do not expect these numbers to be even... You gotta pay for the best! However it seems like these numbers should be a bit closer.
This is not criticism. Just an observation because you asked. I have not even reviewed this discrepancy in my league. But, like I said it was one of my first impressions - that the best players here are not as economical as they might be.
Lastly, this has nothing to do with stats but I figure I'll bring it up - I feel like there's not enough incentive to sign long-term contracts here. My suggestion here would be to install a minimum contract length based on the total contract extension value. This does not need to apply for FA due to the rules about contracts relating to real life (which I really like), but on extensions I think it makes a lot of sense. Here's my rule on that from DNHL for an example.
Contract Limits for Extensions
Contract extensions follow the contract maximum lengths as shown above as well as their own minimum standards.
Salary - Min & Max Years
$6.5m+ - 5 years (the overall limit)
$5 to $6.4m - 4 or 5 years
$3.5 to $4.9m - 3 or 4 years
$2 to $3.4m - 2 or 3 years
$0 to $1.9m - 1 or 2 years
Again, this is NOT criticism. Just some observations. I really like this league so far and can't wait to start scoring!