Basically, a modern infantrist carries the same weight in equipment and weapons as a soldier in full plated used to do. The difference is, the full plate's weight was distributed all over the body so you'd be able to go longer with it on. It did restrict some movements to some degree though, but not quite as much as one would expect. Probably the main disadvantage (talking about comfort) is probably the weather. If it's very hot, a full plate armour with a thick doublet/gambeson/aketon underneath will not be the most comfortable thing you ever did.