Debating space combat between either fleets or individual ships has it's own set of pitfalls which aren't as present in other kinds of matches, partly due to how divorced the fight is from our common sense of scale. Anyway I hate writing introductions so lets get into it.

Acceleration vs Speed

When you think about "speed" for a "normal" character (think like Captain America or Batman or something) people are often thinking some value in m/s which represents their how fast they can move. But with space craft when you think "speed" you should really be thinking "acceleration".

In space there is no kind of significant air resistance, so maximum velocity is only capped by the total delta-v of the ship (aka the total amount the ship can change it's velocity).