This is education, not advice
The information here is written for the general reader and does not replace a personal medical consultation. It cannot tell you how much skin you have, whether your skin will contract after fat is removed, or whether either operation is appropriate for you.
No outcome is guaranteed
No operation can be guaranteed. How much the arm changes, how the scar heals, how long the result holds and how the skin settles afterwards vary between individuals, and a result is judged honestly only after the arm has had time to settle.
Scars are permanent
An arm lift leaves a long scar that matures over a year or more and remains visible afterwards. Arm liposuction leaves small puncture marks. No cream, dressing or device removes a scar or makes it disappear, and anyone describing a scar treatment as though it did is describing something else.
The risks are real for both
Both operations can be followed by bleeding, fluid collection, infection, wound healing problems, asymmetry and altered sensation, and the lift carries a specific risk to nerves running down the inner arm. Revision surgery is sometimes needed and is a separate operation with its own cost and recovery.