Plate mail was a bit more cumbersome in terms of putting it on, getting it off (especially if you needed to go to the toilet lol!) and fighting in it, but again, the soldiers would have been used to it.

Now that the practicality is out of the way, armour is very effective in stopping cuts and similar thrashing blows, chain mail is not as effective in stopping thrusts, which is why plate mail was developed. (I have seen a man stand stock still, harden his abs and absorb a full blow from a semi-blunt arming sword without any effect other than a grunt of surprise)
Seriously, armour was a life saver and the problems associated with it were compensated for by extensive training in strength and technique (like, you know, moving slightly so a blow glances off you instead of hitting you, or dodging it?)

Usually the armoured people in films whom get cut down so easily are nameless, faceless (helmets) grunts who are there to serve the purpose of getting cut down by the main characters – never trust hollywood. (also, read Stormtrooper effect)

Look at the film and if they use muskets it’s ineffective and ways them down. But if they use swords they r wrong