Hmm, with geokinesis I can create elaborate traps and huge titanic buildings that I can hole up in, cities in mountains, etc. In addition I could put minute amounts of earth in peoples pores. Then rocket them inside of their soft fleshy body, form them into a sharpened earth blade, and cut every internal organ up from inside.
However, with Pyrokinesis I can pull an Azula or Ozai, as well as being able to send millions of micro flames at someone to cuaterize their every nerve or cell. Furthermore I could fly, create deadly fire weapons, and even cause natural disasters. If I blasted the ocean enough it could create huge volumes of steam that condense into stormclouds. It wouldn't even need lightning, it could cause torrential rain. In addition I could strategically set things on fire and keep it going to unleash infernos of oblivion that could be used to weaken enemies. There's also the cooking people from the inside factor and giant fire golems. Tough choice.
Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn