Yes, you read this right, I am comparing British Airways Club Europe to Easyjet for a 4-hour flight from London Heathrow to Thessaloniki, Greece and then back.

Cost
BA: Cash £70.50 + Avios 9,750 [cash price was £400+]
Easyjet: £46.76

At the airport:
BA:
Fast-Track not honoured. I had to use the standard queue for boarding. Took 30 minutes+
Lounge: Used Galleries Lounge. The staff unhelpful and rude. Could only stay for a few minutes due to the delays with security.
Boarding: Priority boarding not honoured. Free for all basically.

Easyjet:
No Fast-Track but Thessaloniki airport's security was a breeze. Cleared security in 5 minutes.
Lounge: Used SkyServ with Priority pass (this is also the same lounge BA is using for its business class). Friendly staff but limited food options.
Boarding: I didn't pay for priority boarding, but I could see there were two clearly separated lines one for priority and one for standard tickets. So if you decide to pay for it, it's honoured and worth it since it comes with free luggage on the plane.

On the plane:
BA
Seating: The usual intra-European seats for business class - i.e. Economy class seats. The usual middle empty seat NOT honoured. The passenger next to me decided to bring her son and the flight crew didn't say anything..
Food: All meat options run out, when they reached my row. I've had some very mediocre Vegetarian food. This is the third time that they run out of all the options when they reach my row. I don't even know why they bother giving menus.
Staff: As it's a true tradition for BA now, one of the crew was the best ever and one of them was the worst; full of sarcastic comments and rudeness.

Easyjet
Seating: Same pitch length as BA. Middle seat empty!!
Food: Buy on-board options. I had a reasonably tasty meal that I paid for £8 (20% discount if booked before flight).
Staff: Lovely staff throughout the flight.

Conclusion: While I understand it's not a like-for-like comparison and one flight was from the UK and the other the return leg, I think it's still fair to say that if you would like to have a premium experience, flying with EasyJet could give you a far more premium experience than flying with British Airways Business Class. In this flight, I didn't even pay for any priority seating or boarding and my experience was still better.
If you have millions of Avios to burn: BA. If you want a premium experience: EasyJet.