When travelling from Europe to Asia, what time of day do you prefer to leave Europe? The last two trips I took to Asia were on Singapore Airlines, and both flights left Europe between 11 and 11:30 in the morning, thus arriving in Singapore at 6:30 the next morning Singapore time. The problem with this flight is that you arrive at the time you would normally sleep (around 11 pm to midnight European time). Thus, sleeping on the plane is hard since this feels almost like a dayflight. The advantage is that you arrive in Asia early in the morning, so if you do not have much scheduled for the day, you might be able to enjoy an extra day providing you can go to a hotel and sleep for a couple of hours.
On the other hand, most of the European carriers leave Europe in the evening, thus arriving in Asia mid- to late afternoon the following day. The advantage then is that it will be easier to sleep on the plane since the body clock will be ready for sleep when you are on board. Also, the arrival late in the afternoon the following day means that you do not have to make it through a whole day after enduring a long flight.
Personally I think that both have their advantage. The latter is clearly the best option if you are able to sleep well on the plane, but since I am not a good sleeper on planes (I can not afford to fly anything other than Y), arriving 6 in the morning still works fine for me. Since the flight is also almost like a dayflight I also get to enjoy the IFE far more than I would on an evening flight, since I then would normally be too tired to really enjoy it.