I'm drawn between too options:

Assassin (Dark Elf or Khajiit or Argonian)

-Join Darkbrotherhood
-Join Thieves Guild
-Use daggers

or

Pure Mage (Breton or Dark Elf)

-Join College of Winterhold
-Use mostly Destruction spells


So what would you guys recommend? What are the pros and cons of each?

I don't really want to do a hybrid of anything, I'd rather stick to thePure Warrior/Thief/Mage set. I also don't have followers if that matters.

Race: Argonian.
Class: Bethesda removed classes in Skyrim.

I play a Dark Elf assassin, and it works pretty well (as well as looking totally badass). The 50% fire resistance helps against dragons and the Ancestor's Wrath power will help you deal with tougher enemies that get too close.

I've done both Khajitt Theif/Assaisin and HIgh Elf Destruction/Alteration Mage and both play styles are enjoyable. Personally you are going to sneak alot with the assasin class and sometimes that can be tedious but the satisfaction of taking out several foes without alerting anyone is satisfying. However its also satisfying to get a swarm of NPC bunched up and cast a high level AoE spell. So I'd pick both actually.

Thanks guys. I still don't know what I want to do yet though.

do both. when you get tired of one, just save and then load the other.

Depends on what you prefer really: The Khajiit/Argonian option, in my opinion has a lot more proper adventuring to it... moral quandries, sweaty palms whilst avoiding detection, strategic thinking etc... My experience of the Mages Guild questline was of trying to stay awake through what must be the greatest torrent of verbiage ever to grace a role-playing game - "Ages ago... Great Tome of Whatsit...(fetch quest)... Mysterious Order... Beware the Other Thing...(fetch quest) How dare you meddle with... drone, drone, drone."
Basically, would you prefer 'Casino Royale' with a tail, or 'The DaVinci Code' with pointy ears and a lot more dialogue.

I always make a Bosmer stealth archer as my first toon in any ES game. As for magic users, Bretons get a racial magic resist and some nice magic skill ups to begin with(Speech never hurts, either).

I would say a Khajiit Assassin, They're a bit more fun to start off and I think it's a lot easier to build a good Thief/Assassin than a mage.

Breton for the more magically inclined (DnD style) assassin.

Build

http://skyrimcalculator.com/#57555
5 free perks before level 50. plenty to build the enchant tree if desired.

argonian assassin/thief, dual wield/alchemy/sneak as major (can max) with minor (50 max) of archery/enchant/lockpick/alteration and unarmored.

Same here! It wasn't until my sister started talking about decapitations during cut scenes that I realized what I was missing while using a bow. But it was so satisfying taking out an entire dungeon without ever being spotted that I didn't switch over to one hand until my Archery was at 100.

anyway, I still prefer stealth but I'm also enjoying my High elf pure mage. Not as much, but he's only level 30 at the moment.

I tried using a bow, but I found it pretty boring. Fighting Dragons was so dull as well.