lol it totally depends.
a straight person (such as yourself) will like opposite-sex sex better
a gay person (such as myself and many of the people in this section) will like same-sex sex better
a bisexual person will depend on the individual. some will prefer same-sex sex, some will prefer opposite-sex sex and some will like both equally.
anyways a lot of bi girls i've heard about that say they like sex with girls better say it for these reasons.
1.) girls can have multiple orgasms, thus they can have sex for longer.
2.) girls have the same kind of body as you, so they know what feels good.
3.) girls are more affectionate during sex and are more likely to cuddle with you.
4.)girls care more about pleasing there partner were as some guys just stick there thing in and as soon as they please themselves they don't bother with you anymore. (idk bout this one sounds bias)
anyways i also know plenty of bi girls who prefer guys. most bi people i've talk to though say sex is best with who you're in love with the most, regardless of "equipment" (: