I've been renovating a Searider with serious gelcoat damage (see thread Searider 5.4 Project
Personally I prefer to replace "like for like" certainly if there are chips and gouges to flll or contours to rebuild.
You should not use polyester filler (car body filler) for these repairs as it is resin bulked up with powder which is hydroscopic, so again gelcoat is the way to go.
It looks from the pictures that you probably need to cover the whole of the hull as it will be impossible to blend in extensive gel repairs.
There are some great 2 pack paint systems available and you will probably be happy with the "out of the tin" finish where as re-coating with gelcoat (flowcoat) will require more work.
For gel to be successful it needs an excellent mechanical key so you need to be very thorough in your preparation and use a coarse grit to prepare. Gelcoat will stay tacky in air, flowcoat is gelcoat with a wax additive which rises to the surface during the chemical process and excludes the air allowing the gel to dry as it would in a mould.
The wax needs to be removed (acetone or sanding) before re-applying subsequent coats.
After extensive prep using gelcoat as a filler, I sprayed 3 coats of straight gel onto my prepared hull then finished it of with a final gelcoat with the wax added (flowcoat) to seal. Spraying gel is tricky and requires quality equipment but you can also apply with a roller and brush. Humidity and temperature are also factors so you need to do this indoors or at least under cover, same will apply to most paint systems.
Once applied gel/flowcoat will need an awful lot of flatting off with wet & dry and then polishing with a compound but I believe you get a better more resilient finish. See my thread and website for more info, I will be adding a lot more detail over the next few weeks.