On the sex part, There's that whole stigma which is true, but men biologically are engineered for sex.
On the relationship part, The biggest difference is if you are looking in the longrun…depending where you are (if gay marriage is permissible by law) if you would wanna get married have children, etc things like that. The major problem with gay relationships is cos men think with their dick more than their hearts...not to say that they aren't exceptions but this is generally true to my belief because when you know you have something strong solid and healthy going in a relationship in the longrun...the tendency to stay true to your partner outweighs the temptations of cheating.
Most long term homosexual relationships result in it being "open" or a "dont kiss and tell" policy or some where it becomes polygomous...
(just my personal thoughts to share, i don't intend to offend anyone on their believes)