just an opinion,,,,,
If you've visited a casino and have a favorite game there that you like then I think you'd enjoy having that game at home, whatever brand of machine it is. Over the years IGT has had the largest number of machines installed in casinos, so this means that their machines are often available to a homeowner for a lower price, you'll usually have a bigger choice in what IGT machines you can buy, parts for them are easier to find and typically the parts are at a lower cost. And you'll find more people familiar with the IGT machines to help you if there's ever a problem.
But if you really like a particular Bally (or other brand) game then check into getting it and the machine it plays on. Afterall, the biggest reason to own a slot machine is for the fun it brings you. When you find a machine you're thinking about buying you can always ask here about any known problems or unreliability on that specific model.