AC Generator

It depends on the requirement. But in most cases, AC generator will be preferred over a DC one. DC generator can be useful in cases where you just require a continuous supply of current without any disturbance. But if you want a good quality current to be transmitted over longer distances for significant period of time, go for an AC generator. AC generators are much more reliable and also have longer life durations.

The key difference between these two is slip rings are the rings used in an AC generator for generating AC current. While commutators are used in DC generators to produce DC current. If we talk about the shape, slip ring is a continuous circle while commutator is divided into two halves.

Alternating Current is the type of current whose direction isn't uniform and can change constantly. On the other hand, dc current is the type of current who can have a single direction only. DC is a comparatively low quality current as compared to an AC current.

Based on theory