gel coat
Id go wwith the gel coat not only is it cheaper but it will bond nicely to the glass. Just make sure to sand the edges before you fair it in.
repair
Hey Lady ! Nice scratch ! Whatever ya choose a method I use to speed up the overall process of either one is to tape some saran wrap or even a plst. sac on the outside of the area so once the stuff is applied you then cover it w/the saran to seal it in you want it nice and tight and to conform to the contours o the area . This speeds “kickin” time and whatever ya use it creats a polished smooth glasslike surface . Eliminates sandin and looks good , both ways will work and as long as ya clean the area well you probably will not be goin the 2nd way for quite some time . I always carry some marine-tex w/me for trip repairs . Even repaired seam leaks on old outward bound Grumman canoes with marine tex , so it works on aluminum too .