No I do not think that glue is “more effective” than sutures used for tummy tuck surgery. There are however many factors contribute to the final appearance of a scar after tummy tuck. For example, some patients are prone to develop keloid or hypertrophic scars despite the surgeon's best efforts. Some patients will develop superficial separations of the incision line, depending on the quality of the skin present (for example, stretched marked skin may not “hold” sutures as well as skin with normal thickness dermis).
On the other hand, the surgeon may be able to control the quality of the scar with attention to certain technical details. For example, it is important to take as much tension off the final layer of closure as possible- if tension is taken off the superficial layer (by using deep sutures) the incision may heal with a finer line scar. Avoiding excessive excision of skin may also help avoid tension upon closure of the suture line.
The use of silicone-based products (creams or sheeting) may also be helpful in achieving the best scars possible.
I hope this helps.