The 777 cabin is very pretty and I like the wide seat. Plus you can see easily out of the window. The A380 Suites are spacious, private and the swivel chair with separate bed is next level luxury, but less convenient for looking out of the window (as it is the opposite direction to the main TV (though there are three screens so you do have a choice of viewing angle). And the bathrooms on the A380 are bigger than the ones in my apartment, i.e. more convenient to change into pyjamas. Hard to compete with the A380 overall and I think it's quieter than the 777.
But both are good choices so I wouldn't dwell on your decision