Your mate might consider adding to his stats on win ratios, the one I've just posted about how Liverpool's best of 86 points would have compared with the league winners of the past two decades.
Only twice in the past decade would 86 points have won the league title, compared to EIGHT times in the previous decade and the two it wouldn't have beaten were 42 game seasons. The bottom line is win ratios mean diddly on their own, they need to be compared with win ratios of the era. The quoted stat that Rafa has one of the best win ratios of a Liverpool manager ever sounds nice to those who take it at face value, but other managers with lesser win ratios won multiple league titles to go with other trophies. They didn't have multiple subs to bring on use 25 players in 15 games. Fair enough comparing Houllier and Benitez if anyone, but back when Houllier was manager (and Evans) was when we could have won the league with the points as low as they've been for some time
LIVERPOOL v CHAMPIONS
08/09 : Liverpool 86-90 Man Utd (-4)
07/08 : Liverpool 76-87 Man Utd (-11)
06/07 : Liverpool 68-89 Man Utd (-21)
05/06 : Liverpool 82-91 Chelsea (-9)
04/05 : Liverpool 58-95 Chelsea (-27)
03/04 : Liverpool 60-90 Arsenal (-30)
02/03 : Liverpool 64-83 Man Utd (-19)
01/02 : Liverpool 80-87 Arsenal (-7)
00/01 : Liverpool 69-80 Man Utd (-11)
99/00 : Liverpool 67-91 Man Utd (-24)
98/99 : Liverpool 54-79 Man Utd (-25)
97/98 : Liverpool 65-78 Arsenal (-13)
96/97 : Liverpool 68-75 Man Utd (-7)
95/96 : Liverpool 71-82 Man Utd (-11)
94/95 : Liverpool 74-89 Blackburn (-15) - 42 game season
93/94 : Liverpool 60-92 Man Utd (-32) - 42 game season
92/93 : Liverpool 59-84 Man Utd (-25) - 42 game season
Rafa has the highest win ratio since King Kenny, Kenny won three league titles and finished runners-up three times in six seasons, Rafa has managed to finish runner-up once.
HIGHEST LFC MANAGER WIN RATIOS (LEAGUE, TOP FLIGHT ONLY)
1. 60.71% Kenny Dalglish (titles x3, runners-up x3)
2. 56.10% Rafa Benitez (titles x0, runners-up x1)
3. 56.08% Bob Paisley (titles x6, runners-up x2)
4. 52.38% Joe Fagan (titles x1, runners-up x1)
5. 51.59% Bill Shankly (titles x3, runners-up x2)
6. 51.18% David Ashworth (titles x2, runners-up x0)
7. 49.12% Gerard Houllier (titles x0, runners-up x1)
8. 48.26% Roy Evans (titles x0, runners-up x0)
Tom Watson, George Kay and Matt McQueen had lower win ratios but won the league. Statistically Rafa might be right up there, but only because the stats are incomparable across eras. Maybe managing is tougher these days, but the bottom line is we will never know if truly great LFC managers of the past could win the league, unless of course we tried King Kenny.