First thing you should know about multi-jamma adapters is that they are NOT going to make your life "easier". Most PCBs have very different refresh rates and resolutions, meaning you still have to pop open your control panel and adjust the monitor setting each time you switch between games. You will also have to adjust your power supply voltages to make sure the added draw powers both boards adequately. Oh, and don't even thing about trying to power more than 2 boards without an additional external power supply!
I agree with shmuppylove on those cheap Chinese made "remote control" multi-jamma boards on ebay. You will not only risk damaging your PCBs, but also the power supply in your cabinet.
What I do recommend, is
Mike's Double JAMMA adapter. I've got a couple of these, and use them to run matched PCBs in my cabs, such as Garegga+Batrider, or Ketsui+DDPDOJ. PCBs that are made by the same manufacturer, around the same time, typically have the same resolution and refresh rate. Mike's adapter keeps power to both games, so you don't have to wait for the game to boot up when switching. Switching is done instantly by pressing P1 and P2 start buttons at the same time.