I already have the Blizzbrand and I've been thinking whether I should upgrade my Sealed Sword or make the 5 star of my Blizzbrand. The brandish series are great because of their speed and elemental damage. Sealed sword series are great too because they're strong and all. I could still upgrade my sealed sword if I want to but maybe I will regret it. So I want your opinion about this. Should I pick fast weapons or slow weapons?
Also... I'm using the 4 star of Wolver. Ash Tail Coat and Cap
Minor point: I would call Brandishes medium-speed swords. The really fast swords are the Cutters.
In general, the slow swords have wide sweeps (good for hitting multiple enemies) and lots of knockback (good for keeping monsters at bay in tight rooms). The medium swords hit fewer monsters with less knockback, but produce significantly more damage per second. Also, I think that speed and size are secondary considerations in choosing a sword; your primary consideration should be damage type.
For direct comparisons using data, consult my detailed sword guide.