Depending on your budget I would go for inwalls, simply so you can position them at a better height for listening.
just my opinion but I can`t help thinking that ceiling ones are more for surround sound rather than dedicated 5.1 listening to movies stuff.
Which are the best, well sit down here.................................
How big is your budget

my outlay so far for my inwalls if you were to buy them new today is around £4.5k then you need some good amplification to make them work, Oh and a couple of decent subs £2.5k.
So thats around 9 grand, then you need.....................................
So in other words we need to know your budget, room size and if you have any equipment already.
You can see mine in my thread somewhere but these are really very high end speakers so you might not need/want to go this way.
One of the big problems with inwalls in the impossibility to demo them as well, I was thinking initially about Monitor Audio CP Golds or Kef 9000`s at the time I was looking for some but simply on not being able to listen to any went and got these MK`s and am I glad I did, they are unbelievably brilliant but should be shouldn`t they
good luck and keep us posted Al