Pass first PG's have traditionally throughout NBA history had more success in terms of winning NBA titles then scoring PG's. None of them with the exception of Magic Johnson was really a franchise player but all of those title teams except for Kobe's Lakers and Jordan's Bull's had a key contributor at the PG spot. Dennis Johnson, and Tiny Archibald are examples in the Celtic's past. Both were very good and contributed a whole lot to Celtic's title teams but neither was a franchise player at the time they played in Boston.
There have been 3 PG's in history that were or were arguably their teams best player and that won a title Magic, Isiah, and Billups. I don't believe Billups was the Pistons best player that season, but many do. Cousy was an all time great PG, but was never Boston's best player on the title teams. Clyde Frazier also an all time great.
Isiah was a scoring PG. I don't think there is much debate there.
Billups was a scoring PG. Career best assists 8.6 and only above 7 one other time in his career.
Frazier a scoring PG. First three seasons around or above 7 assists a game, never again above 6 with six seasons above 20 points a game.
Magic pretty clearly a passing PG.
Cousy was a bit of a hybrid. He was a great passer, no doubt, but he also was the second leading scorer for virtually every title team he was a part of and the Celtics loved to share the ball.
When you start looking at players that were top 3/4 on their team that won titles, you get guys like Parker (scoring), Payton (scoring), Archibald (scoring), D. Johnson (scoring), Robertson (scoring), Hollins (scoring), and Goodrich (scoring). Kidd and Rondo are the only guys that would be considered a pass-first PG that were arguable a top 3/4 guy (that wasn't a 1 or 1a).
If you aren't in the top 3/4 of your teams hierarchy then you aren't enough of a contributor to make a difference.
The reality is Magic, Kidd, Rondo, and possibly Cousy are the only PG's that played key roles on championship teams that you would consider a pass first PG. Scoring PG's win far more often than pass-first guys. Even role player starting PG's tend to be more scorers whether it is Fisher (Lakers), Harper (Bulls), Cassell (Rockets), Paxson (Bulls), etc.