Hey Adam, that's great question and im sure not many have the knowledge about the game to give you a corect answer.
In general
Man to man gets you higher tackle number and that's good most of the times.
Stopping their attack right away.. this would make your defense better but also make players lose more condition.
However against stronger teams i would be careful.. since instead of tackle this could generate more fouls.. and that's dangerouse.
Going zonal is safer, going Man to man is risky.
If you've got players in the right position to cover opponent's attack then go with Man to man
for example: He is playing 4-4-2 Diamond (dmc mc mc amc) and you've got 4-5-1 V style, you could use Man to man and put blue arrow on DC DC and DMC to cover his attackers better.
p.s:I'm at work right now so i can't come up with more examples and explaining but i'll do that in few hours

I'll check the top formations and try to explain every setting and the reason why it should be set this way.