many dressage horses can jump sometimes, just to have more atletic back, so any smart rider do both. In old dressage test was a jump! Really, find Caprilli test
I think that a dressage rider will get more pleasure riding a good jump horse than a bad dressage horse and in reverse. So try your horse and try to find his best
It has to be whatever you love more, and whatever your horse loves more. If he ends up being more suited to dressage but you hate it, that's not going to benefit either of you.
I like to try to put in some basic dressage movements to any horse I ride because of how it improves rideability. A horse who can adjust their stride, bend properly, ride corners properly, maintain rhythm, etc. is a horse you will be more successful with on a course. Those qualities, just to name a few, are some of the most basic things you work on in dressage. A lot of dressage horses also do a bit of jumping and gymnastics to keep them fresh and interested, and just as a form of supplementary training.
I would work on both at the same time, and see where they take you. If you guys are more inclined towards one or the other, it will probably become clear pretty quickly, and either way you will have a more versatile and rideable horse for it!
With whatever you decide, dressage is an amazing base for any discipline. It will help with ride-ability, versatility, and athleticism. I'd say focus on dressage, and then consider switching to jumpers/eventing