Which Clippers?

[welsh_mare]

I have decided to treat myself, we have 2 section A ponies which my friends daughters along with my boys ride, with the amount of work next winter i will be looking to clip them, but their coats are thick but not coarse (sp).
Would i need medium or heavy duty?, battery operated or mains?. Haven't bought clippers for years and i am getting so confused by all the choice out there.

Thanks in advance for any answers