Assuming Attack and Move speed were your only Ascendancy considerations, Slayer is very comparable:

Gladiator gets

• 4% Attack and Move from node 5
• 20% Attack and Move from node 6 charges
• 12% Attack from your other three minor nodes (4% ea)

Totalling 26% Attack Speed and 24% Move Speed for Gladiator

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Slayer gets

• 15% Attack from node 10
• 10% Attack from node 3 and 5 (5% ea)
• 20% Move from 6
• 20% Attack from node 6 (assuming Rare/Unique kill within 20s)

Totalling 25-45% Attack Speed and 20% Move Speed for Slayer

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There are certainly other benefits and nodes to consider, such as the value of Bleedsploisions vs Culling and 10%/20% more damage multipliers or Charge generation vs Overleech, but claiming Gladiator has a significant advantage over Slayer in terms of raw speed is questionable.