T vs. A shaped shirt-sleeve cut

[internationalist]

I prefer the T shaped, it's definitely more comfortable if I want to move my arms. What's the reason behind they make so much more A sleeves? (At least in RT, I don't know about bespoke.)

What's your opinion on T vs. A shaped sleeves?

[DFR]

Can you illustrate what you are talking about please - this is no help at all.

[internationalist]

Sure. Can I upload a picture here or do I need to use an external host?

Anyways, here you are:

[Der Zuschneider]

The T-shaped sleeve cap for a shirts is lower than a normal sleeve and therefore allows more movement.

[couch]

Also, the undersleeve is longer on a T-shaped sleeve and so naturally produces fullness under the armpit when the arm is lowered to the side. With a closely cut shirt sleeve and armhole this may not be a problem. As I understand it, on a fuller jacket sleeve it requires a negotiation between the size and shape of the armscye, the angle (close to a T or more acute) of sleeve insertion, sleeve fullness, and degree of drape allowance (if any) under the sleeve to balance freedom of movement (including ability to raise the arms without disturbing the jacket's position) against a "clean" sleeve. With a long undersleeve and a high armhole, greater freedom may tend to result in a fold of cloth in the undersleeve just below the armscye when the arm is down. If this is neat and controlled it may not be objectionable. (But this is one reason why most "modern"--especially RTW--jackets, which are no longer expected to be worn on active occasions, often have low armholes, short undersleeves and/or an acute angle of insertion--this allows a very clean line in and around the sleeve, and (in some contemporary fashions) a very close-to-the-body cut, so that the jacket stays very neat when arms are relaxed or riased only slightly. But they are like straitjackets if you want to raise your arms.

I invite our tailors to correct and expand on this understanding. It's an interesting and inter-related set of issues.

[hectorm]

I prefer the T shaped, it's definitely more comfortable if I want to move my arms. What's the reason behind they make so much more /|\ sleeves? (At least in RT, I don't know about bespoke.)

Are you talking about shirts, jackets or both?
If you are talking about shirts, the T shape (or almost T) is the "normal". I don´t think they make /|\ sleeves in RTW shirts. Although most RTW armholes tend to be lower and bigger, still respect the T general shape.
So I assume you are talking about jackets.
I don´t think any tailor would cut a T shaped jacket (RTW or even bespoke). Once again, RTW armholes tend to be lower a bigger. While bespoke jackets have higher and smaller armholes, they can´t avoid /|\ sleeves either. It´s a matter of degrees in the angle.
One thing I tell you: once you got used to wearing jackets with smaller higher armholes and sleeves joined at your right pitch, RTW jackets indeed feel like straitjackets, as Couch said.
One more thing, to really enjoy the advantages of the small higher armholes in your jacket you should have small higher armholes in your shirt.

[internationalist]

Re.

I'm talking about shirts. And yes, sadly they make a lot more /|\ than (almost) T nowadays.

For a jacket, /|\ is of course OK.

[Bertel]

Very interesting, this thread, I just came across it by chance (couldn't figure out a bit by its title). I am very slim, skinny and slender, my shirtmaker started out with massive /|\ which just looked very wrong with all the creases and extra fabric at the lower sides of my chest - now almost arrived at high narrow armholes and proper T with close fit, so comfortable and well fitted. At first I had thought my request for going very closely towards T was peculiar and just my strange personal taste, good to see relief and support here