a380 - fully flat, direct aisle access, 'mini bar' and a quieter cabin (engine noise)
777 - angled seat, not all seats have direct aisle access, bottle of water, louder (engine noise)

If you read through all the posts some of us will say how rubbish the 777 J seat is and others will say it is not too bad. If you are flying solo and you take a window seat and the seat next to you is occupied the phrase 'climbing over someone' should not be underestimated. If you are capable of supporting your own body weight you can get yourself in to a dip position and jump over, or ask the person to wake up and put their seat back up.

Personally, I would actively avoid the 777 which unfortunately has been difficult to do over the last couple of years with covid. The differences are that much I think there should be dual Business class pricing across the 777 and a380 range.