My major boat project for summer of 2020 was a hull paint job. I hated that yellow mustache that much.
I had previously painted the hull on a 30' sailboat, that had red gelcoat and after 6 0r 7 years had faded and gone chalky. I used Petit Ezypoxy and got a nice shiny outcome. Unfortunately that paint also faded badly during the next 4 or 5 years. It was ugly enough that I ground it off and painted with Interlux 2 part polyurethane. I sold the boat 1/2 way through that paint job, but finished the work before passing the boat on to its new owners. 20 years later I saw it and other than where it had a fender rub that had worn through to the old gelcoat, it still had a good shine and good colour.
More recently I had used Brightside on a portion of the inside of the bulwarks on my present boat. It was better than not painting, but not a fabulous finish, both immediately after painting and about 10 years later, when I was deciding which paint to use for the job on the hull.
I used Petit Ezypoxy again, but this time white. Now 3 seasons in, it looks great. Like you, I am aware of the full value of my boat and though a $50k paint job would look perfect, I was not prepared to pay for "perfect". The paint I used cost $70 Cdn / US qt. One qt did a whole side. Prep was a little body filler for major gouges, a good cleaning with Lysol toilet bowl cleaner for the moustache, light sanding in a few places. I used a brush for the "tipping", though I didn't bother with the "roll" part.
It turned out so well that I went on and did the insides of the bulwarks, including re-doing the piece done 10 years ago with Brightside. The result was encouraging enough I kept going and the only parts I didn't get to are the seat assemblies on the flybridge. Those are covered most of the time with the cushions, so won't rise to the top of the to-do list for a while yet.
$280 for paint, a couple of brushes, a couple of l of thinner, mostly used for brush cleaning, though the paint did need a little thinning when getting near the bottom of each can.
In the result I have about a 4' paint job under most conditions. Occasionally at sunset, the sun will pick out some places that are only a 20' job, but then that is all I was aiming for.
I get more compliments on my "beautiful boat" now than ever before.
No more Mustache!
I doubt there is any real difference between Petit and Interlux. Either should work as well as you need.