You're conflating claims, though.
-To determine best offensive player requires qualitative analysis.
-The most productive is an easily determined quantitative analysis.
I'm not sure there's a single "better" offensive player in the ACC than Harrison Barnes. In the sense that he can score inside and out, he's a knockdown shooter from all over the floor. I don't doubt scouts I've talked to when they've told me that Barnes is going to be an excellent NBA player.
From a quantitative perspective, there are several analyses that we can use. I like to form analysis through a comparing these five, in particular:
1. Top 5 ACC - Points per 40 minutes pace adjusted (>20 minutes per game):
-Stoglin = 27.6
-Scott = 24.8
-Barnes = 24.0
-Harris = 20.8
-Leslie = 20.0
(Next five = McKie, Zeller, Kelly, Henson, and Rivers).
2. Effective Field Goal Percentage [(FG + 0.5 * 3P) / FGA)] (eFG%) (>20 minutes per game)
-MaPlumlee = .62
-Harris = .62
-Scott = .61
-Curry = .58
-Kelly = .58
(Next five = Kadji, Henson, Barnes, Dawkins, and Strickland)
3. True Shooting Percentage [PTS / (2 * (FGA + 0.44 * FTA))] (TS%) (>20 minutes per game)
-Harris = .67
-Scott = .66
-Kelly = .66
-Curry = .63
-Heckman = .60
(Next five = Zeller, Barnes, Kadji, and McKie)
4. Efficiency (EFF) - Privileges post players
-Henson = 21.5
-Scott = 21.0
-Zeller = 18.9
-MaPlumlee = 18.2
-Len = 18.0
(Next five: LoBrown, Rice, Howell, McKie, and Harris)
5. PER - Privileges post players
-Scott = 33.6
-Len = 29.2
-Henson = 28.2
-Zeller = 27.1
-Rice = 26.3
(Next five = Barnes, Kelly, Stoglin, MaPlumlee, and Green)
So, while Stoglin is arguably the most productive, he's hardly the "best" by the numbers. While Barnes is qualitatively "the best," the numbers point towards a guy like Scott (shows up in every category time in top-3) being the "the best."
What's cool is that CJ may be the best perimeter offensive players by the numbers (productivity + efficiency) in the ACC right now... McKie's production holds up well, too.
I always like to compare basic statistical analysis with the eye test when making bold claims like this... The issue with KenPom stats is that nobody actually understands what they're measuring (outside of stats experts and Mr. Pom himself). At least you can explain what you see in this kind of analysis.