Most of the time, T-shirts with crew necklines ("crew" originally referred to the crew and oarsmen who wore these shirts while working on a ship) and t-shirts with "v" necklines can be substituted for each other in most outfits. However, they differ enough that there are certain outfits that work best with each style. The neckline is subtle, but combining it correctly in an outfit can have a noticeable effect.
The main thing to remember with t-shirts, though, is that if it doesn't fit you well, the neckline isn't going to help you.
A t-shirt's fit depends a little on the person's preferred level of tightness and a little on the activity level, but a good rule of thumb is that you should not be swimming in your t-shirt. According to Well Built Style, the fit should be snug but not tight, with the bottom long enough to cover the waistband of your pants and the sleeves hitting mid-bicep.
A crew neck t-shirt has a rounded collar that encircles the neck. The higher neckline cuts off the eye early and draws attention to your body shape, so shoulders get highlighted (and look great) in this t-shirt. Not only do your shoulders look more square, but it also balances out a narrow face and longer necks, according to Bamigo.
A v-neck is what it sounds like: a t-shirt with a neckline in a "v" shape. It came a little after the crewneck. The v-shape frames your face while also visually lengthening your torso. It gives a slight slimming effect as well. On an additional note, pay attention to the depth of the "v" in your v-neck. If you aren't sure how low the "v" should be, err on the side of higher. Please.
Usually, the first t-shirt outfit to come to mind is the classic t-shirt and jeans combination. Either neckline can be worn with jeans. T-shirts are great casual wear and seem to naturally match with jeans when a laid-back feel is called for. It's hard to go wrong with this look at a casual outdoor summer party or a relaxed home-cooked dinner.
Of course, t-shirts aren't limited to jeans alone. The t-shirt is one of the most versatile casual-clothing staples a wardrobe can have. Athletic wear is basically made of t-shirts of one type or another, so t-shirts clearly work well with basketball shorts or sweatpants. When paired with lounge pants, in particular, t-shirts are also great for lounging. There's no better outfit for chilling in front of the TV on a lazy Saturday morning or during a romantic evening in.
The differences between the two necklines emerge when they are paired with an outer layer.
The crew neck t-shirts pair really well with bomber jackets and blazers. The bomber jacket combo is reminiscent of tough military fighters from "Top Gun" and gives off a very masculine feel.
While v-necks can be worn with blazers, crew necks tend to match better because the high neck can also give a more formal feel. The blazer and t-shirt combination is a great dressy casual outfit and can work well in a more informal business setting.
The v-neck t-shirts are perfect for layering under similar v-neck cardigans. The double "v" visual works in a way that is more effective than the crew neck/cardigan pairing. Additionally, the v-neck is critical for the subtle undershirt. Undershirts shouldn't be visible beneath the collared overshirt, so v-necks are perfectly suited to serve the purpose.
Now that you know how the different necklines on a t-shirt can subtly alter the way you look and how these seemingly minor differences can affect certain outfits, you can be more intentional about which you choose to wear and when. Whatever the occasion, when the fit is right, the neckline works, and the outfit is chosen with care, you can go about your business comfortable, casual, and confident that you look good.