Firstly, the raw numbers need some minor adjustment.
The Bulls are a slightly faster team than the bucks (about 1%), so I inflated the Bucks and Jennings Assists and FGM by that amount.
Pace Adjusted Bucks FGM 2351, Assists 1348
Raw Bulls FGM 1796, Assists 1256
Secondly, Players can't assist their own Field Goals (well... technically speaking they do, but not in THAT way).
So we remove the FGM of each player from the total number of FGM for each team.
Pace Adjusted Bucks FGM 2351 - Pace Adjusted Jennings FGM (352) = 1998
Raw Bulls FGM 1796 - Rose FGM (537) = 1796
Thirdly, taking raw team FGM is pretty misleading, as neither player is on court for 100% of the time. So I did a big fudge, and assumed that FGM are distributed evenly over the course of the game. Rose is on court for almost bang-on 75% of the court time. Jennings is still a rookie, and is also at the mercy of the feared Skiles rotational hook, so plays 33 mpg, which is around about 68%.
Adjusted by played minutes:
Bulls FGM - Rose FGM (1796) * Rose game percentage played (75%) = 1347
Pace Adjusted Bucks FGM - Pace Adjusted Jennings FGM (1358) * Jennings percentage played (68%) = 1359
Right, so these are the made field goals which our two players could theoretically have had an impact on. So how do they stack up?
Well...
Jennings had a pace adjusted 382 assists of a roughly-estimated 1359 made field goals, so had a direct impact on 28% FGM.
Rose OTOH, had an actual 352 assists of a once again roughly estimated 1347 made field goals, directly impacting 26% FGM.
So, generally pretty close, with an edge to Jennings. Not the full story, of course. How much impact does each player have within the context of team offence?
Well... pace and minutes-played adjusted, the Bucks had 916 assists whilst Jennings was on the court, for which he was responsible for 42%. If an assist was made, it was reasonably likely to have been on the end of one of Jennings passes.
(NB: This suffers from the same (inherently dodgy) logic that all assists are distributed equally over the course of a game rather than being bunched in the time that the star PG is on the court. Sue me.)
For the Rose Bulls, they had 942 assists whilst Rose was on the court, for which Rose was responsible for 352, or 37%.
(For reference, by the above logic, Steve Nash assists 47% of the made FG and is responsible for 71% (!) of the Suns assists made whilst he's on the floor)
So it's reasonably clear that Jennings assists a larger percentage of field goals and that more of the Bucks passing game runs through him than it does Rose.
Now how do the offences as a whole stack up. Firstly, raw numbers:
Bucks FG% = .436
Bulls FG% = .448
The Bulls are a better shooting team by a reasonable margin. The Bucks certainly aren't making their current run on the basis of a pulsatingly efficient offence. However, once again if you're looking PURELY at assist performance, you have to take a player's own shooting out of the equation.
Bucks FG% - Jennings shooting = .452
Bulls FG% - Rose's shooting = .438
So yes, you're dead right that Jennings does appear to have a reasonable amount more to work with than Rose does. For kicks, however, I also calculated Team TS% (I'm not sure if this is in the SLIGHTEST a reliable or usable stat).
Bulls = .516
Bucks = .516
THEN, when you remove the PG's shooting from the calculation, it looks like:
Bulls = .513
Bucks = .527
A small trend downwards for the Bulls without Rose, with a full percentage point spike for the Bucks.
I'll be frank and admit that I didn't think the difference would be quite so obvious (despite the caveats that are my spreadsheet skills and basic statistical understandings). The edge Jennings appears to have as a distributor is counterbalanced by the apparent superiority of the rest of the Bucks roster.
A very, very good post from poster rravenred displaying just how little offense is present in the Bulls offense minus Rose. Rose averages fewer assists per 36 (I think a full assist less), and has an assist rate about 2% lower than Jennings. Jennings doesn't even play on a GOOD offensive team. Just a meh one.
And yet the result is pretty evident: you do get a significantly higher amount of assists next to better players. Even when your role is similar (both Rose and Jennings handle the ball in similar situations, with players that they defer to, and with secondary ballhandlers present on the team.
The effect isn't vast--"if guys only hit shots, Rose would average 10 assists"--that's not valid, but it does have a real impact. However, if we want Rose to be more than a 6.5 assist player, it's actually how we use HIM that we have to change, not the amount of shots other guys hit. Rose isn't the PG on a laaaarge amount of possessions, which is just not how other star PGs are used.