What play style do you think is the most fun and why?

Stealth assassin with occasional healing spells and whatnot. Dual wielding is amazing and relentless and the power attack for it is nasty. Stealth characters have a great utility of being able to deal amazing damage and ever since Bethesda made it so that you don't instantly become detected when you attack someone it makes stealth epic. You can lob a few arrows at someone before they discover your position and effectively kill them before you are discovered. Been playing on Expert and having little problems with that. Fus Roh Dah your heavy armored opponents and run in and start power attacking and swinging wildly and get the advantage. If you do that you will gain a heavy lead in the fight even though you are using light armor.

Best and most fun are two different things.

Best on a technical level: Heavy armor dual wielding warrior
Evidence: http://www.gamesas.com/index.php?/topic/1266212-2469-armor-3199-damage-using-smithing-alchemy-enchanting-only-31-perks/

Best on a personal fun level: Heavy armor mage focusing on destruction and conjured weapons.
Evidence: Undeniable fact that magic is cool.

i enjoy stealth so fun sneaking around and sniping people from afar
well i find it fun