Your question is difficult to answer because no operation is necessarily “better” than another; every patient's situation is different and demands its own “solution”. In other words, patient A may be an excellent candidate for a full tummy tuck operation whereas patient B may be an excellent candidate for a mini tummy tuck operation.
Having said that, generally speaking, the mini tummy tuck is an operation that produces very limited results and is very rarely indicated. It involves a shorter incision but does not address the majority of the abdominal wall issues present for most patients who present consultation. For example, the area of skin excised is quite small. The abdominal wall musculature is addressed below the umbilicus leaving the upper number wall potentially lax. The appearance of the umbilicus is not necessarily addressed sufficiently.
For most patients who have had pregnancies and/or weight loss a full abdominoplasty is necessary to achieve the desired results. Of course, there are downsides (including a longer scar and probably a longer recovery time) but for most patients the benefits outweigh the downsides. It is not unusual to see patients who've had mini tummy tuck surgery present for revisionary surgery.
For more precise advice addressing your specific situation, seek consultation with well experienced board-certified plastic surgeons.
I hope this helps.