I've always played a female Altmer but this playthrough I am considering being a male Altmer. I was wondering what kind of NPC dialogue changes happen? From what I heard sometimes the changes can be dramatic.

Oh and please feel free to be specific, I'm a spoiler junkie.

I have noticed nothing big, just your basic swapping of pronouns. Have noticed many more dialogue changes based on race

There are a few comments that are different, one of the maids at the blue palace makes comments if your male about a Knight in Shining armor whisking her away, while for a female character she asks if you need a traveling companion, there are a few other similar swaps in dialog but over all its minor.

Aww. Oh well I may as well make both. Thank you

Next to nothing really.

as it is skyrim you are playing, you can assure that no matter what you do you can experience the whole content of the game ;D

Whoever told you that certainly wasn't talking about Skyrim, or any TES game for that matter.

The biggest difference is when I'm playing my female I'm constantly aroused.

If you're a girl you wear funny looking armor. Well, funnier than standard for a fantasy ... nvm.
Plus there's the while marriage thing.

Every mariable character is bisixual so no real difference there either.

Nothing much. Most of the dialogues are neutral to begin with

The best advantage you get for playing as a female is the availability of a lot more (armor) mods to you, if you're on PC. Especially the ones from Hentai. That guy is just the manifestation of "art"

Most people who works on armor-related mod starts with female first. Even the could-be-neutral (and awesome) Crown Helmets mod started out as female-only