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 far round your laxity goes, whether the bulge you are concerned about is skin or fat behind the muscle, or whether either operation is appropriate for you.
No outcome is guaranteed
No operation can be guaranteed. How much the body 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 body has had time to settle.
Scars are permanent
A tummy tuck leaves a scar low across the abdomen and a body lift leaves a scar round the waist and back. Both mature over a year or more and remain visible afterwards. 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 both carry a risk of a blood clot. The larger operation carries the larger risk. Revision surgery is sometimes needed and is a separate operation with its own cost and recovery.