Different seat- some are high up giving and excellent view, some are lower down meaning easier to play, some recline more or less, some are more padded... if you have an issue ERF, just as if you have an issue with anything with parenting, really, there will be a whole bunch of people who cannot wait to solve it in some way.
But there's nothing more disheartening than having that conversation, using your knowledge and goodwill, when someone has already made their choice, and is happy with their choice.
If I spend time asking for details of your car, your child, your seat currently, what you've tried, and then suggest a few, are you really going to go to a shop to try them, try them out with your child, big up to your child how great they are, and buy a new, probably non-isofix seat?
I don't think so. So it's easier if you say 'I've decided on isofix, and against ERF'. Because now you have a thread recommending good belt-fitted seats, and ERF seats, but you don't actually want them, because you want isofix, and not ERF! Frustrating all round.