exceptions for flow control is bad

bad_controller.rb

class BadController < ApplicationController
  def create
    begin
      some_object.save!
    rescue Error => e
      render :json => { :error => e.message }, :status => :unprocessable_entity
    end
  end
end

best_controller.rb

class BestController < ApplicationController
  def create
    if some_object.save
      #do normal rendering logic here
    else
      render :json => { :error => e.message }, :status => :unprocessable_entity
    end
  end
end

better_controller.rb

class BetterController < ApplicationController
  def create
    begin
     some_object.save!
    rescue ActiveRecord::RecordInvalid => e
      render :json => { :error => e.message }, :status => :unprocessable_entity
    end
  end
end