In terms of custom armour, Excalibur pisses all over the Lord of the Rings saga. Armour was a huge percentage of the budget on that film and it looked magnificent. :)
A bit overdone really, but I don't know of any other film that has matched it. (I'm sure there exist some, but I don't know of them)
Zardoz was just weird... It seemed as if a lot of big stars were doing weird movies back then that required them to run around in leather undies... But even so Zardoz was off in its own little weird corner doing its own weird thing.
Excalibur is lush, thick and sumptuous, but more conventional I think.
I wrote a paper on Excalibur for my Medieval Studies "Arthurian Romance" class. Lots of meaning in there and pure magic that is at the core of the Matter of Britain. The king and the land are one. Excalibur wraps up all the loose bits of Arthuriana into one coherent story. Then there's the use of Wagner and O Fortuna.
Zardoz was a gag from his reading of Wizard of Oz. ;) He should have waited and bought the movie rights to Wicked or Son of a Witch lol!