But if you wanted to make a stab at it, I would say that CP has one double digit rebound game in the last two years to RR's 9. That's 1 out of 5 games for CP = 20%. RR has 9 in 38 games, or 26%. Yes, there is a difference there as well, but it isn't huge, and since it isn't a "core function" of a PG to rebound, I would continue to hold that Rondo's rebounding edge is insignificant as a deterimining criteria of who the better player is, or, put another way, I don't think Rondo's edge in rebounding is significant.
So since most centers are poor passers you'd discard that criteria when you compare Walton or Divac or Sabonis to other centers? Rebounds equals possessions for your team, and having more possessions than your opponents is fairly important. The fact that other point guards can't rebound like Rondo doesn't mean it's insignificant, it means it's a big advantage for the Celts.
At the risk of being redundant, the numbers are rather clear that although RR is a better rebounder, CP is very nearly as good at rebounding at Rondo is, and that holds up any way you look at it. And while Rondo gets around 10% more rebounds, CP's advantage in just about every other category more than makes up for Rondo's slight edge in rebounds. In fact, though Rondo grabbed 0.4 more rebounds than CP during last season, he turned it over 0.6 times more often. You are correct, those extra possessions are important, and the edge still goes to CP.
Should I bring up the fact that opposing pgs had about 1 more turnover a game vs Rondo than they did vs Paul last year? And it's worth noting that Rondo ups his rebounding in the playoffs while CP doesn't. And I don't dispute that CP puts up better stats. But Rondo plays with better players. Put Paul on this team and his numbers drop. Put Rondo on a team like the Hornets and his numbers shoot up.
First of all (if I can say anything "first" after so much has been offered already), it is completely awesome that we have a young PG locked up who is so close in comparison to the best PG in the game today. As we go on (and on...), that's the thing, as a C's fan, that really stands out.
Breaking down what you've got here, though, here are my thoughts:
Yes, Rondo's opposition had more TO's last year, probably (not sure) due to his steals, though CP was coming back from injury and did, actually, lead the league the previous two years and was perhaps superior to Rondo for the reasons Roy mentioned a while back. No clear edge there.
CP upping his game in the playoffs: see above response to Nick, who I gave a TP for noting that Rondo is clearly a gamer, while CP may or may not be, as he hasn't had the playoff opportunities that Rondo has, and hasn't been LEFT WIDE FREAKIN' OPEN like Rondo was much of the time.
As far as numbers changing re: talent of the team, I would say that, like the Big 3 when they came together, CP's counting numbers would drop, but like the Big 3, his (already superior) percentages and efficiency would improve, which would only further the advantage to CP. By spreading the floor better than RR (or, to say, spreading it at all), the rest of the team's offensive percentages and efficiency would likely improve notably as well, and the importance of that really can't be overstated. Further, it would add some roster flexibility, since there wouldn't be a shooting range litmus test for FA or trade pickups.