Should I attack mounted triangle or arm triangle from mount?

Attack the mounted triangle when you can climb and figure-four your legs around the neck with one arm trapped; attack the arm triangle when you can lock head-and-arm with your shoulder and clear to a side angle.

What if they defend the neck but leave an arm?

Use the arm exposure. Arm triangle wants the trapped arm across their neck; mounted triangle wants that arm inside your leg structure while you climb.

Do these connect to technical mount and armbars?

Yes. Failed triangle climbs often create technical mount and armbar chances; failed arm triangles often return to side control or mount with better isolation.

Mounted triangle vs arm triangle: which head-and-arm finish?

Comparison

Choose the mounted triangle when you can climb and close your legs around the neck; choose the arm triangle when shoulder pressure and a side angle finish the head-and-arm squeeze.

Decision tree

Both finishes trap the head and one arm. Your height on the body and available angle choose the branch.

A mounted triangle uses your legs as the strangling structure while you stay on top. It is strongest when you can climb high, keep one arm trapped, and lock a clean figure-four without losing the mount seat.

An arm triangle uses your shoulder and their trapped arm to compress the neck as you slide off to a tight angle. It is strongest when the head-and-arm pocket is already formed and you can clear your hips to the side without giving up the pin entirely.

Mounted triangle cue

You are high on the chest, one arm is inside your legs, and you can throw a leg over the shoulder line toward a triangle lock.

Arm triangle cue

Their arm is across their own neck, your shoulder can replace the missing space, and a side slide tightens the pocket.

When to choose each

Choose mounted triangle when climbing to S-mount or high mount is available
Choose arm triangle when the head-and-arm pocket is already formed lower on the body
Favor mounted triangle when you want to stay on top through the finish
Favor arm triangle when the cleaner path is sliding to a shoulder-pressure angle
If either stalls, improve isolation or switch to armbar instead of forcing a flat squeeze

Common mistakes

Both chokes fail when people squeeze before the structure is closed.

On the mounted triangle, the common error is crossing the ankles before the shin clears the neck. Climb, cut the angle, then lock.

On the arm triangle, the common error is staying square on the mount and hoping shoulder pressure alone finishes. Clear the hip angle and keep the trapped arm glued.

Retention still comes first. If they are bridging you off, return to the mount retention basics before hunting either choke.