Surgebinding because
A) magic (baseline abilities from inhaling Stormlight)
B ) magic (Surge A)
C) magic (Surge B )
D) comes with a friend!
I'm not entirely sure about that last part, the spren could be not nice. Privacy would be a factor. Hmm... but the Nahel Bond isn't as bad as some other fantasy magic via bonds to magical creatures. I guess it might depend on my hypothetical potential Bondmate.
Sandmastery is so limited. Do not want to be a Dakhor Monk or a Bloodsealer, way too morbid. ChayShan seems pretty limited too. Forgery is nice, but honestly, Surgebinding just has a wow factor to it! Awakening comes with the Heightenings, of course, and that's nice but I'll still prefer the Surges, giving up parts of my Breaths to animate something sounds like it'll feel terrible, don't like the idea of collecting Breaths at all either if that's a consideration in this hypothetical scenario. The Metallic Arts are cool too but again, I would prefer Surgebinding, maybe being Fullborn might tempt me. I'd pick AonDor when someone cracks using it off of Sel perhaps, but before then, it's definitely Surgebinding!
1st choice: Surgebinding (depending on how I get along with my spren)
2nd choice: AonDor
3rd choice: Feruchemy
4th choice: Allomancy
5th choice: use Hemalurgy to get all of the above four! Mwahahahahaha!