I think the midcentury nickname of Phil prevents more people from considering this distinctive classic, it makes me hesitate too as Dr. Phil does come to mind, but I likely will still use it as I love the full form Phillip & nicknames Pip, Pippin, Flip, & Lip. I do favor the double L, it looks more complete to me, but also our surname has double letter in the middle as well so the alternative would look strange together, in my opinion.