Dear Mushi,
Generally for a long haul flight I would request the front most seats with a bassinet but for a four hour flight the utility of doing this would be questionable. Personally I like the aisle seats as I feel I am not so fenced in but then again it is not so private for breastfeeding.
From all the research I did for flying, as well as a article given to me produced by the Victorian Health Service in Australia, it suggests that you have the baby suckle or suck a dummy on take off and more importantly on landing to avoid middle ear problems related to the cabin pressure.
I have done loads of travel with a young baby, long haul too and it has not been an issue. The air stewardesses are usually more than happy to hold my baby when I need to use the bathroom even! And don't worry about the baby crying, planes are soooo noisy others seriously can't hear that much and generally if they see you are trying to quieten your baby empathise. Good Luck!