When I was young, I wore what I was told to. That was almost exclusively t-shirts. As I got older, I realized there is a variety of shirts, and the t-shirt was the most casual of all. I began to notice people wearing t-shirts as outerwear that were clearly meant to be underwear, and all t-shirts became underwear to me. Dress shirts looked professional, and hid some unwanted curves.
As the years went by, I came to realize that wearing a button-down, usually dress shirt, was not projecting the image I was going for. People would comment on how my clothing choice was unnecessary, as though I had gone to some lengths to button a shirt. Or how uncomfortable I must be, as though a shirt that buttons is less comfortable than a shirt that doesn't.
I can't say I get it, but I don't need to. I'm certainly not going to chose clothes that I need to convince people they like. I'm trying to wear clothes that people think look good on me. I moved on to hoodies, and the infamous t-shirt. I watched some youtube videos on men's style, and picked up some interesting, and good advice.
First of all, t-shirts as outerwear have a shorter lifespan than other shirts. They're more prone to looking faded, torn, and even just start getting clear or discolored in the armpit area over time. They need to be replaced more often, but they're fairly inexpensive, so that's not a problem.
As a general rule, v-necks are more likely to be made to be worn as outerwear than crew necks. You also have to consider the weight of the fabric, the color, and it's transparency, of course.
Another big one for me was size. The seem at the shoulder should line up with your shoulder joint. This one isn't true of any t-shirt I own. They truly don't make t-shirts that would have fit me at shoulder blade, and at my belly. But that was in the before time.
My chest is 44 inches, but that's mostly muscle. My belly is not gone, but certainly endangered. I've worn XL shirts as far back as I can remember, occasionally moving up to 2XL, depending on the brand. Now I see larges, and even mediums, fit my shoulders, and that's all that matters in a t-shirt when I have so little to hide. I'm even finding the cheap yet fashionable asian cut clothing online will fit me. Suddenly the world is my oyster.