興奮するWhen both can let themselves go and you're in the flow without much communication. Then it all depends on the mood... sometimes slow and with love, other times fast and hard... it always depends on what you're in the mood for at that moment
興奮しないWow, there are a lot of things... If the hygiene isn't right, one of the two doesn't really feel like it, if you're not on the same wavelength, too much spit, too much pain,... oh there's more, just ask :P
好きな体位Definitely doggy! Love to be fucked from behind :)