The A1200 is a great retro gaming machine. It's able to play a lot of games without a lot of hassle. Plus, it's small, has AGA, has an on-board IDE controller, has a PCMCIA slot, etc. So it does have enough modern stuff to help you obtain games and files for it without the trauma and expense you'd encounter with a simple A500 only.
Of course, if you're wanting to play with some old video editing, the 1200 is a terrible choice. It's underpowered, has no video slot, is in an enclosed small chassis, poor power supply, etc.
Your best choice for a machine is all decided by what you want to do with it.