I choose the simbot. You can control it, and make it do whatever you want. It is useful for creating sculptures and take photos of the family, along with portraits. I always make an all-rounder robot who can overcome any situation.
As for butler, I hired a butler for my Roman Villa, and made a room for her in the backyard. I don't know why she doesn't go there, and keeps drinking coffee for energy. Probably I didn't give any way back to her room, I mean I mistakenly made the passage impassable.
Well, for most time, I choose butler. It is cheaper, easier to get, and I always wanted a servant in my household. But sometimes he/she cooks food even when someone is not hungry, and stock up the fridge with leftovers. My fridge is totally smelly by now. Also I got a Kleptomaniac butler, who swiped away my things when he was alone in the room.