You correctly say: "While some studies do show a negative effect, there are others that show a positive effect, and the majority show no significant difference.", and in support, you cite "sexul effects of circumcision" in Wiki. However, if you bothered to read the Wiki studies, you would find that about 90% of the males researched in those studies elected circumcision in response to a foreskin problem or complaint (most commonly phimosis). So how are these men's testimonials relevant to the issue of newborn or infant circumcision, which removes NORMAL, HEALTHY foreskin?!
Removing painful foreskin (e.g. phimosis) may well improve sex by at least making it bearable, but it will give no indication as to the effect of non-therapeutic circumcision.
In reality, those Wiki study results are terrible for circumcision, for in spite of being CORRECTIVE (therapeutic) circumcisions, in most cases the men reported no improvement. If a corrective operation does not result in significant improvement, the result is surely poor. In any case, they are irrelevant to newborn circumcisions.