Is there extra legroom?
I note Premium is the first two rows - but when you try and book standard economy, rows 1-6 are blocked out and can't be reserved. Are they waiting for uptake and then possibly increasing premium to row 6 if it proves popular?
The only differnece I can see is you get an extra 5kg hold baggage and drinks. It works out an extra £200 for 2 of us in June, its cheaper to book standard economy, add on all the extras (meal, seats etc) as I don't think you'll get anymore leg.