preferable, more preferable, most preferable

Because preferable already means “more desirable,” it is redundant to write more preferable and most preferable.

• She found it preferable (not more preferable) to convert her overtime hours into leave.
• In this case, the preferable (not most preferable) option would be to update the policies and distribute them to all the branch offices.

However, such phrases as far preferable and greatly preferable are acceptable.

• Henry found it far preferable to put off until tomorrow what he could have done today.
• The use of renewable energy sources is greatly preferable to that of non-renewable ones.