Rosenbogen > Bibiki Seashell
Simply because 10HP > 1VIT @ Endgame
Unless you are fighting NMs of the Aquan class.
You should buy this when you reach 70 with your PLD. Also it's fairly cheap these days so it's not a big deal to afford this great bow!
Adding to the list of competitive bows, Arco De Velocidad provides the same HP boost while exchanging the VIT+3 for STR+1 and regen (1/tick) during the daytime.