I don't think the products matter that much if you use them right. There are lots of fine products out there. The time and methods you use are what matter.
How bad is the finish?
If it's really bad you may start by wetsanding.
1000 grit wetsand
2000 grit wetsand
rubbing compound w/ wool or foam pad on buffer
polish with foam pad on buffer
wax by hand
That's how I prefer to work. All those steps should be able to revive any gelcoat. If your gel isn't that bad start with a later step.
Last year I removed the decals from my boat and wet sanded where you could see the ghosting.
Then machine compound, machine polish and hand wax.
This year I hit some bad spots with rubbing compound by hand. The machine polished and hand waxed the boat.
Currently I've been using mostly 3M products but in the past I've had good luck with other brands as well.
3M Marine rubbing compound
3M Marine Finesse-It II Glaze
3M Marine Cleaner Wax
Collinite Fleet Paste wax
Wipe down with Hot Sauce spray
The 3M cleaner wax is liquid and goes on quickly. I use it sometimes for a quick wax job. The Collinite last longer but takes a bit longer to apply. Also since it's just wax I usually try to polish the boat before using it, typically once per year. ;
The boat is a 2004 Malibu and is stored outdoors during the summer. Sometimes I leave it in the water for a week or two at a time to get the most out of my $20 launch fee on our local lake.