Neither rack and pinion or ballscrews is more powerful. It just depends on your gearing. You're entire drive system needs to be matched together to work the best. You should take into account what motors you plan on using when you make your selection?
Personally, I think rack and pinion is a much better choice for a 4m axis.
For a ballscrew that long, I'd use something 32mm-50mm in diameter, with a 32mmpitch, and a fixed screw with spinning nut.