Hello fellow Anons! Kiwi here to provide basic educational facts about various actuators we can use for gifting artificial avatars of our hearts desire motion!
1. Let's start with a personal favorite, the impractical, inefficient yet oh so fascinating: Heated Twisted Nylon! 
What are they? They're nylon threads which have been spun around then annealed to seal in their coils. A heating method causes these threads to then contract or expand.
Good: Why is this a personal favorite? Simply put, it's natures muscle substitute for muscles. To elaborate, this marvelous unvention contracts like human muscles, has a similar practical strength/weight/volume as human muscle. Icing on this proverbial cake comes in its incredibly low cost of manufacture. Materials needed are nylon threads and a heating element. A fixture for production can be produced simply, operated with incredible ease, all while having a low cost. It very well could have revolutionized all of robotics if it weren't for its flaws.
 
Bad: This is honestly a terrible actuator. Its greatest flaw comes from its speed. they aren't as fast as human muscles unless they're underwater. Water reduces efficiency to unacceptable levels if they're powered by batteries. Water is also rather heavy. If used, you'd have a waifu that moved slowly , would seize up in hot weather, and her battery would die rather quickly. Final nail in the coffin: it's very difficult to get positional control. 
2: Pneumatics, moving her booty with air!
What is it? Pressurized air is guided to an actuator where its energy turns into motion. Popular air actuators include rotary turbines, cylinders, and air muscles.
Good: Actuators are light for their power. Positional control isn't difficult to attain. They can be faster then human muscles. Heating elements can be used to augment performance to higher levels.
Bad: These things require electrical actuators to function properly. Thus, they're inherently more complex then electrical counterparts. They need a source of compressed air, either from a tank or a compressor and a tank. Compressors are large, heavy, noisy, all around unsuitable to be incorporated into a waifu. Air tanks would also run out rapidly unless she's barely moving. Overall, they're suited better for industrial use.
3. Hydraulics, they're like pneumatics except stronger, needs a return system, needs an onboard pump, gets hotter, generally costs more, and is heavier.
(2 and 3 are great for stationary machinery which requires high power as they're very cost effective as high power actuators)
4. AC motors
What are they? They're rotary devices which use AC current to create magnetic flux used to provide torque. 
Good: Generally highly efficient with good thermal characteristics. Can have controllable speed and torque. 
Bad: They run off of AC electricity, batteries don't provide that. It's not difficult to change DC to AC but, it's a layer of extra cost and complexity. Overall they're great but the next actuator is better suited for our purpose.
5: DC motors are the ideal actuator for smaller waifus.
What are they? They're actuators which convert DC electricity into rotary mechanical energy.
Good: They're inexpensive, easily attainable, and simple to control. They're very easy to control. Uses DC which batteries provide.
Bad: Need to be geared down to provide good torque. They're middle of the road efficiency wise. 
(For smaller waifus, their lower efficiency compared to the next actuator isn't a major concern. Smaller batteries recharge rapidly, so having her need to charge in her bed isn't a big deal.)