A rotary mower with a four stroke engine is the best.....without a rear roller if the grass is uneven.
Hover mowers are ok on bank sides, but they still catch obstacles!
Only if you have to mow bank sides where the engine is at an angle for extended periods is a two stroke machine needed.
Plus it also depends on the amount of lawn you have to mow. A self-propelled petrol mower is a definite boon if you've got a big expanse but a hover (assuming electric here) is quick and easy on small areas.
If the lawn is very uneven a hover might catch on the high bits and scalp the lawn so you could end up with some bald patches. Also you don't have control over the cutting height with most hover mowers and over time the lawn can become clogged with the thatch (trimmings) unless it has a collector so occasional raking might be needed to remove that.