If you're doing a familiar style of character, go Ranger/Wizard. If you want to PrC either side, make sure you maintain all good saves and full BAB. Familiars benefit from your skill ranks, base saves, BAB, and total HP, so while a nice HD is useful, it's absolutely the lowest priority on the list.
If you happen to be Chaotic Good, then Exalted Familiar gets you a Coure Eladrin, which has Dancing Lights at-will that can be turned into Silent Image at-will (so, so abusable). Also obviously an Outsider, so lots of Polymorph options and free Martial Weapon Proficiency.
Imps and Quasits are both also good for their Commune ability and Outsider typing. They also have 3 HD, so they get two feats instead of one.
Mephits come in behind the fiends, but there aren't any moral or ethical complications in having a mephit follow you around. Wyrmling Dragons are about on par with the Mephits because they're completely customizable and can easily bring 3-4 feats.
That said, if you can get it admitted, you WILL use a Silvanshee familiar (Pathfinder SRD). Even if it's Lay on Hands ability is converted back to 3.5e Lay on Hands, especially if it's ability to cast Stabilize is converted to Cure Minor Wounds, you WILL use it, because it could quite possibly be the best familiar EVER.