Is an iron condor always preferable to doing a simple credit spread

They are two completely different trades and should be used for different purposes.

If you are doing a credit spread you (should) have an opinion about market direction and the spread will benefit from you being correct. Also, remember that with a credit spread (bull call for example) the underlying price can go up and up and up to the moon and you will always just collect the maximum credit. This will NOT happen with an iron condor.

With spreads you can collect your max credit to the up or downside based on the type of spread, as long as it goes the direction you bet on. With condors you want the underlying to be range bound, or more specifically, not to exceed the short strikes of your condor.

So you would want to do a bull put or bear call spread when you believe the market can move in a particular direction AND you don't need to worry about how much it is likely to move in that direction. So if you were bullish on a new tech company it would be fine to put on a bull call spread, if it shoots up 300% tomorrow you are very happy...if you had a condor on at the same strike(s) you would not be very happy and would likely have lost the maximum.

Which strategy to use depends on your outlook for the market. The iron condor will provide a larger credit but has the potential to lose in both directions.

Either vertical spread used in the iron condor will have a lower credit and larger potential loss but can lose in only one direction.

IRON CONDOR

The iron condor is a neutral strategy for when you don't expect a lot of share price movement. It can return the maximum profit even if the underlying security moves a little in either direction.

The iron condor spread has four option legs where you sell an OTM bearish call spread and an OTM bullish put spread, generally with the short strikes equidistant from the current price of the underlying.

The iron condor generates its maximum possible return when the underlying security trades between the short strikes and all 4 legs expire.

The maximum loss is the difference between the strikes on the losing side less the total premium received.

CREDIT VERTICAL SPREAD

A credit vertical spread can be either a bull put or bear call spread. For ease of discussion, let's consider a bear call spread.

The ATM or OTM bear call spread is a strategy for when you don't expect a lot of upside share price movement. It can return the maximum profit even if the underlying security doesn't move at all.

It generates its maximum possible return when both options expire OTM.

The maximum loss is the difference between the strikes less the total premium received.