I recently responded to this question on a public forum (EliteTrader:

Why are vertical debit spreads (bull call & bear put spreads) not discussed much? Instead, it seems that Iron Condors and credit spreads are the preferred topic. When you consider the risk/reward ratio of a debit spread vs. a credit spread, especially if both of which are about 2 or 3 strikes otm, it seems that the preference would be a vertical credit spread because of the risk/reward.”

It’s true.Iron condors are a popular strategy and many blogs discuss this strategy (unfortunately including those that want to charge high fees to teach investors how to trade them).

As far as credit spreads and debit spreads go, the reason both are not discussed equally is there there is no need to do so.When the underlying asset, the strike prices, and the expiration are identical, then buying the call spread and selling the put spread (both bullish plays) are equivalent.

For example, these trades are equivalent:

Buy 10 RUTMar 490/500 call spreads.Pay $X
Sell 10 RUTMar 490/500 put spreads.Collect $10 – X

[If you can collect $4 for the put spread, don’t pay more than $6 for the call spread.In fact, don’t pay as much as $6 because you must pay interest on the $600 cash required whereas you could be collecting interest on the $400 cash received.]

By equivalent, I mean that:

The potential profit is equal
The maximum loss is equal

At any RUT price, when the settlement price (RLS) is determined on expiration Friday, the profit or loss from either position is equal to that of the other.