On times, it's Faith by a mile. By everything else it is quite close.
However you got to remember that Faith missed a year to pop out a baby and still came back 15 months postpartum to get silver. I'd also be willing to bet a fair amount of money that in the next two weeks Faith has an extra two world titles to her name compared to Sifan.
Faith | Sifan
Age:
29 | 30
World Records:
3 | 0* (1 if you count hour on the track)
PBs:
1:57.68 | 1:56.81
2:29.15 | 2:34.95
3:49.11 WR | 3:51.95
4:07.64 WR | 4:12.33
14:05.20 WR | 14:13.42
Honours:
2 x Olympic Champion | 2 x Olympic Champion
2 x World Champion | 2 x World Champion
3 x Diamond League Champion | 2 x Diamond League Champion
2 x World/Olympic Podium | 3 x World/Olympic Podium
Head to head (discounting heats):
Faith 9 vs. 6 Sifan
Head to head (just World or Olympic finals):
Faith 4 vs. 1 Sifan
The only World/Olympic final head to head Sifan won was 2019 in Faith's postpartum season.
The arguments for Sifan that would attempt to outweigh the head to head and PB advantage Faith has is range/versatility/doubling. If this were a conversation on who was the most versatile or who is the better marathoner then right now it would obviously be Sifan hands down. In some respects the triple hurts Sifan as it obfuscates her true potential in Tokyo in the 1500m. I think this conversation swings decidedly in Sifan's favour if she had skipped the 5000m in Tokyo and done just 15/10 double. Maybe that's less fun and people like that she did the triple, but had she done that and won it would be 3 Olympic titles to 1 in favour of Sifan.
This sport is all about running fast and winning. Faith has run faster, and won almost every single race that matters against Sifan. It's really tight, but I give advantage Kipyegon.
I would again say that while this is close, given current form + Kipyegon's explicit goal of eventually going after the marathon, I think when both are retired it will be clear advantage Kipyegon.