STI vs Delegation

Rails
1

Hi,

This is my recent project where is started to use STI for extend my Ad
model. I never before used STI and many people which i recently discuss
not recommended me to use this method.

  1. What are the advantages and disadvanteges of STI and why i should use
    delegation ??

  2. And how in delegation i can separate validation like below?

Ride coordination board: Singe Table Inheritance
Database: ads
:title
:price
:content
:username
:from
:to
Model: regular AD
:title
:price
:ad_content
:username
Model: Ride AD
:title
:price
:username

:from
:to

STI:
class Ad < ActiveRecord::Base
validates_presence_of :name, :email, :price
validates_presence_of :title, :ad_content, if: is_regular?
validates_presence_of :from, :to, unless: is_regular?

def is_regular?
self.type.nil?
end
end

class RideAd < Ad
end