Playing 5e with a Rogue. To make a long story short: In my possession I have both Studded Leather armor and a Breastplate. With my 18 Dexterity, My AC with Studded Leather is 16 (12+4). But if I don the Breastplate, my AC is the same: 16 (14+2). Since neither have any disadvantage on stealth or DEX throws – what confuses me is what the difference is. My character has the money to pay for training and doesn’t need cash to the point where I need to hawk the Breastplate for coin. Nobody in the party needs it, and so the question remains:
Is there really a difference between them at this point?
Is the choice cosmetic now? Between a Rogue wearing spiked leather padding all over – or a dense plate with free-flowing arms and legs otherwise? It can’t be this simple, there has to be another angle to it that I’m unaware of. There’s no reason for a piece of medium armor and Light armor to be statistically identical.
Is one truly wiser a choice than the other? If I swap out my Studded Leather for a shiny new Breastplate, is there anything else for me to worry about other than another 7lbs on my person?
Right now, they’re the same. But at some point, you’re probably going to want to raise your Dexterity up to 20, and at that point, the studded leather will be worth 17 AC (12 + 5), whereas the breastplate will still be worth 16 (14 + 2).
More generally, as you say, there’s no reason for a piece of medium armor and Light armor to be statistically identical. But in general, they’re not. They’re identical for you, currently. For a character with 14 Dex, the breastplate is superior. For a character with 20 Dex, the studded leather is superior.