Simple sit on mowers are generally best for smooth, flat lawns. The one's that look like a mini tractor are more rugged and can cope with bumpier terrain but won't be good on real slopes as they can topple.
You can buy them with grass collectors, without grass collectors or with a mulching action which chops the cuttings up really fine and leaves them to feed the lawn. We have one without grass collection as they always seem to get clogged and I spent more time unblocking the tubes on the old one than actually mowing. Friends have the self mulching model and it is excellent but their grass is less lush than ours.
Our new one is a Lazer. It cost about €1000 3 years ago and should last 10 or 15 years. I could have got a robot for the same price but OK was agin it. I'll get one next time though as our grass area will be reduced in the next year or so.
