Depends on what you need. The ESP8266 has a lot of limitations depending on what you want to do. It doesn't have any internal memory, so is dependent on an exte

Depends on what you need. The ESP8266 has a lot of limitations depending on what you want to do. It doesn't have any internal memory, so is dependent on an external flash device. It only has a single adc channel, so if you're doing an sort of measurement operations, you'd need a breakout board of some sort. It requires an external clock crystal, again increasing the BOM. It's also not 5v tolerant, which is useful in some applications. There are definitely a lot more compelling micros out right now, but AVRs still have a lot of tricks up their sleeve that other micros can't meet yet.