If we are talking about best coach of
all the time, then it has to be Sir Alex Ferguson or Bob Paisley for obvious reasons.
If we are talking about it in this moment, I think I would go for Klopp before Guardiola and here are my reasons for it:
1. Guardiola worked in teams with big budgets and many superstars. On the other hand, Klopp started in tier3 team Mainz, then moved to Dortmund who was struggling at the time and made them strong force both in
germany and in Europe. Needless to say he didn't have big budget in both of those teams. Now, he is manager of Liverpool and with basically 0 net spend, he qualified for champions league two years in a row + Liverpool plays the final of that competition in a few days.
2. If we look up their head-to-head matches, we can clearly see that Klopp is the only manager in the world who managed to beat Guardiola on various occasions and he has the best winning ratio against him of all managers.