There is original, and then there is 'good enough'.
Original Galaga Joysticks are leaf switch, and will not give any 'click' when you move them.
Personally, good enough is a 60 in one or one of the emulators. The click of the joystick doesn't detract too much from the game, and Galaga plays really well on the 60 in one and MOST emulators, including MAME setups.
Original will have a picture tube.
Remember TV repair shops? You'd see them in most every city. That was because tube televisions broke... a lot! And they needed to be repaired by someone who wouldn't kill themselves on a 20,000 volt tube that holds a charge potentially for weeks after you unplug the tube.
When you buy original you'll eventually be dealing with tube chassis repair.
Galaga cabinets were a 1981 thing, so your parts are likely 41 years old. Try keeping a 41 year old car repaired, and you are in the ballpark of what it'll take to keep your 41 year old video game repaired.
Burn in is a very real thing on older galaga picture tubes. I would try to make this a cash-on-the-glass transaction where you can examine the picture tube for burn-in before you buy it. Don't buy a machine over the internet on promises and pictures and expect to have a pristine machine. Trust but verify.
Finally, I wouldn't buy a Model T Ford if the nearest repair guy was 400 miles away. Make sure you've got a path to getting your machine serviced. Galaga isn't much fun when it's broken.
60 in ones - good enough, new parts, depending on which garage someone made it your 60-in-one can have good quality parts, or absolute cruft that shouldn't have been in the garbage, let alone sold to a gullible customer. I'm happy with 60-in-one.