full vacuum of a very large table

Got a situation where a 130 mil rows (137GB) table needs to be brought down in size to  10 mil records (most recent)
with the least amount of downtime.

Doing a full vacuum would be faster on:
 - 120 mil rows deleted and 10 mil active (delete most of them then full vacuum)
 - 10 mil deleted and 120 mil active. (delete small batches and full vacuum after each delete).

Any other suggestions?

Thanks,

Nic