Thirty Seasons. In a Sox Therapy thread about the possibility of getting Soriano to play 2B in Boston, "SG" writes: "I've been running some Diamond Mind sims with Dan Szymborski's ZiPS projections disk, and here are the results after 15 seasons":

                 Yankees     Red Sox

Avg Wins:          99.6        98.5

Avg Losses:        62.4        63.5

Actual Win%:       .615        .608

Pythag Win%:       .619        .614

High Wins:          113         111

High Losses:         71          81

Avg Runs Scored:    906.5       882.1

Avg Runs Allowed:   710.7     [blank?]

High Runs Scored:   988         939

Low Runs Scored:    822         823

High Runs Allowed:  776         798

Low Runs Allowed:   670         629

Division Titles:     8           7

Wild Cards:          6           5

Missed Playoffs:     1           3

SG's comments: "Obviously, these don't mean much, but it's kind of interesting to look at. It looks like the Yankees are projected to be a little better on offense, and a little worse on defense (pitching + fielding). About one game separates these teams, even after getting Rodriguez. As Joe C. said, the Yankees may have the higher ceiling, but the risk of implosion is also greater. ... Incidentally, Rodriguez averaged .291/.380/.550 [and] 41.7 HR, with a low of 32 and a high of 51. Best Avg. was .348, worst was .254 (think Steinbrenner would like that?). ... OK, I ran another 15 simulations, putting the total at 30 seasons. Here's the AL East data" [he includes all 5 teams in the thread]:

                  Yankees    Red Sox

Avg Wins:           99.9       99.2

Avg Losses:         62.1       62.8

Actual Win%:        .617       .612

Pythag Win%:        .620       .617

High Wins:          113         111

High Losses:         76          81

Avg Runs Scored:    905.4       884.1

Avg Runs Allowed:   708.7       696.2

High Runs Scored:  1022         939

Low Runs Scored:    800         823

High Runs Allowed:  780         798

Low Runs Allowed:   654         629

Division Titles:     16          14

Wild Cards:          11          13

Missed Playoffs:      3           3

99.9 to 99.2?!? That is close. ... Also, I have to read up on Baseball Prospectus's PECOTA system [I didn't pay that much attention to it last season], because it sure loves the Red Sox pitching staff.