Far more important than the technique is the skill and experience of your plastic surgeon. Choose your surgeon rather than the technique and let them explain why one technique may be better than another.
See the below link on some suggestions on finding the most qualified Plastic Surgeon for a consult.
Your description of 40 pound weight loss as well as having a hanging abdomen strongly suggest that you would most likely need a TT. But, you should consult with a Board Certified PS to be certain. Good luck!
From this picture, it is not completely apparent if you would benefit from SMART lipo which would remove the residual fat while also providing a modest shrinkage of skin. Forty pounds is not massive weight loss and usually does not require skin removal. Find a plastic surgeon and have any in person consultation.Best wishes
Great job on your weight loss. Doesn't appear to be residual fat. Your skin integrity stretched out when you were heavier. Go on a consultation or two to get opinions on your remaining skin. You may benefit from a tummy tuck if there is enough excess that bothers you.
Congratulations on your weight loss. If you've just lost a substantial amount of weight I would recommend reserving judgement on your abdominal appearance for at least another 6-12 months. Perhaps over time to tone will continue to improve.