Colin,
I think as far as premiums go, they’re very similar, they use same or similar pricing models. However, there are some differences between the two. ES options have a multiplier of 50, whereas SPX options have a multiplier of 100 (so you’d have to do 2X size for ES options). ES is American style options, SPX is European. I’m not sure if ES options have the same treatment as SPX options do, for tax purposes.. One advantage ES options do have is margin requirement for selling naked options. Personally, I try to find the path of least resistance, I also want to keep things as simple as possible, so I havent really looked into trading ES options as an IC income trade.