Chrome will still be faster even if ublock doesn't block as much as FF does. In fact the new declarative filters will most likely be faster than the current ones.
In the same way that a car is faster if you make it lighter by removing parts that aren't technically needed to drive down the road :) Airbags, ABS, Crossmembers? Meh.
How much faster does it need to be? I have some complaints about FF, but not on the account of speed. I don't care about microbenchmarks, for me it works fast enough to not notice any lag.
Besides, I really don't care how fast it it when displaying ads and tracking me. I'd prefer not to see them, thank you very much.