Depends how serious you want your jumping/dressage to be. Friesians are not the best horses for dressage. You can do some low dressage with them but for going higher you'd have to find a super talented horse with excellent movement and lots of room as friesians don't really have any (and that one would be probably amazingly expensive too). They do look good in dressage and I guess that's what makes people think they actually are good in it. They're just not built for it. Though the lighter the type, the more suitable for dressage if you after all do decide to do dressage with a friesian (I don't want to discourage you, I'm riding dressage with my friesian too but I know what takes warmbloods weeks takes us months and we'll never get where they will anyway). But if you want to jump, that's one thing friesians are definitelly not suitable for. But I guess you know that. Overall if I were you I'd definitelly go for a DWB as with such a horse it doesn't matter what you decide to do in the end, whether jump or ride dressage, he will be suitable for both more or less equally. And even if you decide to do one and later find out that's not what you wish to do in the future, you can just switch to the other. If you get yourself a friesian for dressage and later find out you won't be able to do it with him, you don't have many other options to do other than buy a carriage or have a cool looking trail horse.