Hi
@RudeDogg1.
What you go for should depend on what you're going to polish, how much of it you anticipate doing and the environment you have available for doing it in. I'd go with
@DRD's suggestion if you're mostly doing small to medium size playfield parts. Perfect for regraining ball guides. That 1hp beast suggested by
@lukewells will make light work of lockdown bars and side rails, but ask yourself how often you're really going to be doing that? And personally, I wouldn't want to put hands anywhere near that whilst trying to hold on to small parts.
Also, consider your workspace. A bench polisher really needs a good sturdy bench or heavy-duty stand to bolt it to, which takes up valuable workspace even if you have got a bench and/or shop. I haven't so clamping a drill into a Workmate-type portable bench is ideal and, as recommended by
@Judge Dreads, means it's easy to set up outside. And do get a mask.
The other advantages of going for the drill option are a) you've probably got a drill already, b) a drill polishing kit is only £14 for the 4" x 1/2" kit:
http://www.metalpolishingsupplies.co.uk/pro-max-steel-stainless-steel-9pc-metal-polishing-kit/, and c) you can work the other way around, e.g., clamp a lockdown bar into the Workmate and hold the drill to polish it.