Both of these are so far the only 2 coaches in the world to have ever won the most prestigious international competitions both for clubs and for National teams.
Lippi won Champions League in 1996, and have been runner up for 3 times. He also won the Intercontinental Cup, now known as FIFA Club World Cup in 1996. Most importantly, he led Italy to win the World Cup in 2006. Some may argue that Italians cheated in order to win, but that's not the point.
Del Bosque, won 2 Champions League for Real Madrid, one Intercontinental Cup and most recently the 2010 FIFA World Cup.
Juventus and Real Madrid are not the same anymore when these 2 left their clubs respectively. Especially Del Bosque, Real Madrid failed to reach the last 8 of the Champions League for the last 6 seasons.
So, in my opinion, Del Bosque is the best, since he won the Champions League twice.
Lippi won Champions League in 1996, and have been runner up for 3 times. He also won the Intercontinental Cup, now known as FIFA Club World Cup in 1996. Most importantly, he led Italy to win the World Cup in 2006. Some may argue that Italians cheated in order to win, but that's not the point.
Del Bosque, won 2 Champions League for Real Madrid, one Intercontinental Cup and most recently the 2010 FIFA World Cup.
Juventus and Real Madrid are not the same anymore when these 2 left their clubs respectively. Especially Del Bosque, Real Madrid failed to reach the last 8 of the Champions League for the last 6 seasons.
So, in my opinion, Del Bosque is the best, since he won the Champions League twice.