1 - Hip hop is not really a "musical genre", but rather a sub-culture. Rap is the actual musical genre of Hip Hop, while Break Dance is the dance, DJing is the art of scratching on the turntables, and Graffiti is the art of painting... These are the 4 main elements of Hip Hop...
2 - If someone blatantly describes Hip Hop as a musical genre, then he won't need to add Rap, and vice-versa, since theres no way in hell you can distinguish them.
3 - Like KRS-One said: "Rap is something you do, Hip Hop is something you live."
4 - I picked Rap. Although I'm a very eclectic listener of music in general, I feel that rap is my favorite musical genre, and definitely the one I dig the most. Always in the mood to find some new underground artists, some rarities, and a lot of oldies, specially from the golden age.