Which is better?

gistfile1.rb

  t = Collection.arel_table
  where(t[:public].eq(true).or(t[:user_id].eq(user.id)))

# or

  where('public = ? OR user_id = ?', true, user.id)

@intjonathan thanks, that's a good point; building arbitrarily complex queries is pretty hairy with that second form unless it's just AND

Can you give an example of nice use of arel?

Not an issue in the simple case, but I believe that the second form will follow/respect/use aliasing of the table (as AR does sometimes with associations).