Smolderdash upgraded very well.  I am surprised I haven't heard more people taking about her.

Sun Forger is going to be the path of choice for those who really like the concept of her flame whip and dividing up the Super Giant sun.  You also get a bump in Critical Hit.  I think this might be slightly better for PVP.

Sun Forged is my path of choice.  As always, when Speed or Armor is tied into a path, 95% of the time I will prefer it for that reason.  That said, Solar Blast is more effective to me and despite not being a fan of Sun's Core overall, it is a nice aura ability that you can control more precisely.  I think this path would be better for story mode than Sun Forger.

Ultimately, Smolderdash upgrades very well with just the base enhancements.  You can't go wrong with either path...You ultimately need to pick if you want Critical Hit or Armor and if you like Super Giant or Solar Blast better.