Either side of the neck? That's what I've always done -- pulse points on wrists and legs always come after the neck with me, and the sides of my neck get scent even if nothing else does. Works beautifully for me. It also works for me to apply my scent under my arms, just after any deodorant (ancillary or not). In very mild weather, I might not even put on deodorant, opting instead for a spritz (or daub) of scent only.
Can't empathize with your experience of D&G and Pi, as those are two of the strongest scents (both in terms of sillage and longevity) in my wardrobe. Oh, well -- each person's body chemistry IS unique.
For example, my other half tried on Gaultier² today shortly after I did. (That was around 1 P.M., just after we had left an 11 A.M. showing of the hilarious Borat.) I can still smell my Gaultier² spritz on my wrist, and it's now 11 P.M. here. HIS spritz of Gaultier², though, first started to fade around 3 P.M., and had faded completely by 5 P.M. (Go freakin' figure!)
Try Lagerfeld Photo if you want a long-lasting warm scent for cold weather -- Photo's one of those scents that lasts and lasts and lasts -- and lasts. and then lasts some more. and then lasts a while longer just for good measure . . . Seriously, I love Photo SO much, but seldom wear it simply BECAUSE I can't get it to away without a serious shower and at least 8 hours of sleep afterward. (And even then, I can still pick up whiffs of it the next day. Kouros is often the same way with my body chemistry, as are M7 and Erolfa.)