【face to face】 —

1. addressing smb. directly:

• There are some students who are shy and will only talk to you online, but others would rather talk 【face to face】 .

2. in direct encounter with a person:

• She toadied to her superiors when she really came 【face to face】 with them.

【head to head】 —

1. in direct confrontation or conflict:

• On the same day the two candidates go 【head to head】 in their only joint televised debate.

2. competing so closely that the lead is virtually indistinguishable:

• He made an announcement saying that the two candidates were 【head to head】 so it wasn’t time to celebrate yet.

Note: The expression does not correlate in meaning with its formal French counterpart tête-à-tête—a talk in private with only two people present:

• He had tête-à-tête with Maung Aye, the powerful Burmese army chief, when he visited Thailand.