the answer will be brought down to the same old advices.
Match on enemy's damage type weakness, such as piercing vs wolvers + fiend, shadow vs jelly + gremlin, element vs construct + undead. Avoid normal damage type at first since they have less damage in general and higher learning curve needed to use them optimally.

CTR is irrelevant, most swords have about the same time to finish their charge. The only noticeable exception is gran faust.
If you want a fast charge but in low budget, then consider a trinket slot with CTR sword trinket.
Slow swing = more ranges, even it's one swing you can hit up to 4 enemies at once, compared to fast swords with fewer enemies, most likely just 2 enemies.

Here is my favorite considering their damage type. They are also 3-hit sword/not really slow sword: (overall, disregard any special case like using volt edge on shock theme, warhammer on vana)
Element: volt edge (spam the charge mostly, shock helps a lot especially mecha bots in arena then I use normal swing for 1 vs 1)
Shadow: acheron (same as above, except the shock part)
Piercing: final flourish (pure highest piercing damage)

Some boost may benefit more on a sword than another, in my opinion:
CTR based swords: brandish line, divine avenger, calibur/fov line
ASI based swords: gran faust, flourish line, cutter line, warhammer, troika line