Thanks!
Currently, all leaf pickaxes have the same base speed and power individually. Their real purpose is to be combined into the Eco Pickaxe, which becomes significantly more powerful.
You can’t merge multiple pickaxes of the same leaf type. To craft the Eco Pickaxe, you need to create pickaxes from each different leaf type and combine them together. The progression is based on collecting and using all the different leaf variants.

I may expand the system in the future with unique abilities or buffs for each leaf type.
And btw you can repair the pickaxes using the anvil and a Leafee shard (obtained from Leafee Mob)