What is the advantage of swivel front casters on a self propelled lawn mower?

I'm looking to replace my old self propelled lawn mower. I got 15 years out of the old one. I want to get the same out of the next. I'm intrigued by these swivel caster front wheels on some of the rear wheel drive (RWD) self propelled lawnmowers. Do they really handle better around objects? How about straight line performance? How reliable are they compared to fixed wheels? Thanks.