The 2-4-2 layout in economy in the A330 is nice, 3-3-3 as used by MyTravel not so nice. 3-3-3 layout typical in economy on the 777 is okay other than 3 seats which are neither aisle or window - 3-4-3 on a 777 as used by Emirates fits into the 'MyTravel' class of comfortable i.e. not very.
Business class entirely depends on the airline - 2-3-2 on an airbus is more cramped than 2-3-2 on the 777 - but most airlines do 2-2-2 business class on the airbus (not emirates).
Emirates use 2-4-2 on their airbus (332's) and 3-4-3 on the 777's - if you ask pretty much anyone who has flown on both in the Emirates fleet - im pretty sure all would prefer the A330.
Personally dont really have a preference - probably the Airbus purely because of the seat 2-4-2 layout - less chance of not getting a window or an aisle seat !!