D&D 5E - Bronze and Brass Dragons vs. Iron and Adamantine Dragons: Which do you prefer?

Just something inspired by a positive thread I read on 4e D&D's MM2... amongst the many, many changes that 4th edition made to its monsters was to take two of the traditional Metallic Dragons, the Bronze and the Brass, and to replace them in the core MM with two new ones; the Iron Dragon was a tough, forest & gully-dwelling brute of a metallic, sort of the metal dragon counterpart to the Chromatics' White Dragon, whilst the Adamantine Dragon was a deep-dwelling metallic of great power and rarity, superior even to the Gold Dragon in some ways, but focused on the Underdark. Both Bronze and Brass did return in the Metallic Draconomicon, but their place as "core metallics" was given over to Iron and Adamantine.

This was ultimately changed back in 5th edition, as was almost every other damn thing that 4e did, but it's left me wondering: what do people think of the two? Do people prefer one pair to the other? Or can you actually enjoy both of them equally? Would you rather have Bronze and Brass, or Iron and Adamantine?

Speaking personally... I'd rather have Iron and Adamantine, hand's down. The Bronze and the Brass have never made a lot of sense to me, nor have they ever interested me - they're freaking copper alloys, and it shows; visually and mechanically, they're more tweaks of the Copper Dragon than anything really unique. One was, I think, a really mercenary dragon eager to amass treasure, whilst the other was a petty warlord who claimed a just cause - I can't really remember them, so maybe that's only their 4e versions.

Iron and Adamantine, on the other hand... for starters, they just sound a better fit; I mean, which feels more organic to you? Adamantine/Gold/Silver/Copper/Iron? Or Gold/Silver/Copper/Bronze/Brass? The Iron Dragon filled a very unique role by being the Metallic's "savage", the embarrassing low-tier brute that the others try to pretend doesn't exist, ala the Chromatics with the White Dragon. The Adamantine Dragon, meanwhile, gives us a truly fantasy metal to base a dragon on, and is unique with its thunder blast breath weapon and its ultra-durable hide.

Anyway, that's my opinion. What's yours?