Blinn-Phong gives bigger highlights but that's not a disadvantage because you can just choose a bigger power value. Phong shading is maybe slightly better looking but while the difference is quite noticeable I don't find Blinn-Phong to be less realistic.
Blinn-Phong is less demanding on the pixel shader. If you are limited by the pixel shader (which is usually the case) I'd go with Blinn-Phong. Also, with Blinn-Phong you can move the halfvector calculation to the vertex shader.