Depends, enchanting would probably get you the best results since Enchanting + Smithing together is possibly the most OPed thing in the game (no joke) but alchemy does supply lovely potions as well.
EDIT:
With most of the 1H tree filled out for blade (in a sword + shield combo), this is the rough/estimated damage rating a deadric sword has -
A normal Deadric Sword gives a damage rating of about 37 Damage.
An upgraded Deadric Sword with 100 Smithing and Deadric Perk gives about 75 damage...
an upgraded Deadric Sword with 100 Smithing, fortify smithing +125 (5x+25 fortify smithing enchants) and Deadric Perk gives about 105 damage
On top of this, now add in, I believe 5x 40% fortify 1-handed weapon effects... the uber 105 damage sword, now has a damage rating of 315... and just to add insult to injury, add on 37 points of frost and fire damage for another 75 points of damage (~200 charges from a grand soul gem). Even on Master Difficulty I do not believe there is much in the game that can survive nearing 400 damage attacks all that easily... make it a standing power attack for the power attack damage and the +25% damage from the savage strike perk and you're probably OHKOing ancient dragons.