There is no simple answer to this question. The two types operate on different principles and therefore may respond differently to various conditions. Some advantages to each type are set out below:
Fastest type to respond to flaming fires.
Lowest cost and most commonly sold.
Some models have a hush or temporary silence feature that allows silencing without removing the battery.
Some models are available with a long life battery.
Notwithstanding these differences, to achieve ULC listing, both alarms must be tested to the same standard and meet the same requirements. Photoelectric smoke alarms may respond slightly faster to smoldering fires, while ionization alarms respond slightly faster to flaming fires. Since you can't predict the type of fire that will occur, it is difficult to recommend which is best. Both alarms will detect all types of fires that commonly occur in the home. Installing both types of smoke alarms in your home can enhance fire safety.