There are two schools of thought here.
In fact, when Clark Gable, the “King of Hollywood” doffed his dress shirt in “It Happened One Night” and revealed that he wore no undershirt, sales of the item dropped 40% almost overnight. And that was in the midst of The Great Depression.
There are good reasons to wear an undershirt. It was originally worn as an extra layer providing warmth. This is still the case with the “singlet” (“Wife beater” or “A-Shirt”), the classic t-shirt and the long sleeved version (a “Henley,” thermal top or silk long underwear.)
The classic version that the late Mr. Brando seems intent on displaying as outerwear, is in white cotton. It has the advantage (especially in summer) of absorbing perspiration and keeping your custom shirts from deteriorating or staining more quickly.
Choose a v-neck to wear under open collars, the crew neck to wear with a shirt and tie or under sweaters. Choose the singlet to display your ink (and request a very low waist, long rise, wide leg and embroidery for your trousers.)
Regardless of style, you want the comfort of 100% cotton, and the right fit. Many men wear t-shirts that are too big for them and create more padding around their middles, blousing out shirts and undoing all of our best efforts at making you appear trim and elegant. T-shirts hug the body, comfortably.
In winter, you may choose to wear silk long underwear as Mr. George Hamilton admits to doing. It is lightweight, regulates your temperature well and may obviate the need for your topcoat if you’re simply jumping in and out of your Town Car or the taxi and dashing inside to the controlled environment of today’s modern office building.
Leviner Wood carries a line of classic, 100% cotton t-shirts in both v-neck and crew neck styles. As the old television commercial put it: “Never let them see you sweat.”