If you are 1 Defence the best armour would be iron. If you are higher than 5, it hsoudl be whatever you can wear.
The best armor to wear in Runescape I would say is Bandos, mainly because a nice combination on Strength bonuses with Defense.
Members: granite armor Free players: rune armor
If you are a member on runescape them you should get Guilded Armor or Gunthix armor. If you are not a member i suggest that you get Rune Armor. (Gold plated armor dose not change the strength of the armor at all) Hope This helps =)
There is no "best" armor in runescape, but armor such as the "nex" armor (Torva, Virtus, & Pernx) are some of the more elite types. Nex armor is dropped by the monster Nex in the gwd.
Granite armor is the best armor to wear with 51 defence members.
Just like everything else in runescape, saradomin is the number 1 best armor in runescape since it is the most expensive. 4-5 mil
Full Rune.
The best ( but most expensive ) has to be armadyl.
Void, because in the long run, void would provide more ranged strength bonuses when actually firing projectiles.
gold armor is called gilded armor in runescape and is gained through treasure trails
Proselyte armour.
Probably the Rune battleaxe, though the Warhammer is slightly stronger against plate armor.