I would say it is likely possible but it is fairly short.
It often takes more than 15 minutes between landing and getting to the airport buildings. EasyJet does not often use bus transport from the plane to the building but it can happen. And when it does it may add more time.
As you say you will need to leave the secure area of the airport, collect your luggage and go through luggage drop off, passport control and security.
Waiting for your luggage should not take too much time, but 10 minutes is the least to expect.
Most of the time non of the lines on the way in will be long, but three times 10 minutes will eat up most of your time. And it is not unlikely there are more delays when things go wrong.
Add the walking times, and you are almost out of time without any delays.
EasyJet can be late, they do not promise to get you there on the minute, just to get you there. With the later flight out of Schiphol, a delay of a few hours will not be a problem, but with the early flight a 30 minute delay can be too much.
I would go for the later flight, 6 hours in Schiphol is not too bad. If it is more than 6 hours you might consider going out of the airport if your incomming flight is on time.
I guess KLM city hopper will not allow you to change to a later flight without paying costs if the EasyJet flight is late.
If the tickets are cheap you could buy a ticket for both the early and a later flight.