Appreciate opinion.
Would be better to apply new gel coat or just paint hull ?
Anyone done it ?

I haven't done it, but paint was applied by the PO about 20 years ago. It started coming away with the bootline masking tape during slips about 8 years ago and is now getting worse in other areas. I think I'd prefer faded gelcoat.

Cheers, Graeme

Apply new gelcoat - It's not a common technique. I did have a friend who was building a cat who would roll on flowcoat and then sand it and polish it. It seemed to work well but it was only for interior furniture. But why? Even if you could do it then you will still have all the problems of keying in a new surface to an old surface. If the original gelcoat is worn through by too much sun and polish then why not paint?
Painting topsides is one of the best jobs you can do on a boat. It's easy to do the prep properly, you just need to get to love your sander and have a wekk or two. Then you apply epoxy primer and sand to a nice finish - then you need some technique or some help for the important last bit. I went through this on a post a week or two ago - search for my posts. It is so much easier than deck paint.

Don't forget vinyl wrap. There is a neglected vinyl wrap boat near me and it has held up well over the years.

On boats I've owned - I have done both re-sprayed Gelcoat and on another re-spray 2 pack polyurethane. Both require a lot of prep and an extreme amount of sanding for a perfect finish. Gelcoat is at least a 1/3 to 1/2 as much more work to get perfect over 2 pack polyurethane. But with some elbow grease you can make it look new again.