At the end of the day, all the systems produce pure water that is fed up a pole, through a brush and onto the window.
No one system will clean a window any better than another (cold water systems anyway) its just purified water pumped up through a brush.
Ionics equipent are first rate, you ARE buying quality kit, highly polished and professional in all aspects, it's unlikely to let you down, and there is backup and warrenties in place if it does.
But it won't make you clean windows any better than any other system that produces pure water, that bit is down to you.
Regards,
Ian