They are designed for different operations, although leisure batteries are now also having to do the work of a starter battery on occasion; power movers on caravans are a typical example. So leisure batteries now can also have a CCA (cold cranking amps) value in their specs.
A starter battery is designed to push out a large amperage for a few seconds to start an engine. This can be in the region of 200 amps or more.
A leisure battery is designed to release its power more gradually. So the leisure battery is better for us to use.
However, I know of several cleaners who only use starter batteries and they have had good service from them. One local cleaner has 2 batteries, one leisure and one car battery. He uses one one day and the other the next.
The car battery lasted a couple of years last time round and the leisure battery lasted another 6 months longer. By the time he took the battery's initial cost into consideration (the leisure battery was more expensive) there wasn't much between them.
We have had good service from leisure batteries and I see no reason to change.
If you are going the car battery route, then Banner Batteries are about the best you can get, but they are more expensive.