Depends whether you're trying to stop the rule to length or the die itself for partial presses. The linear stage will be far more rigid and likely better longevity, but the ball screw will have some backlash that would need to be programmed out and you'll need to keep it greased. An OpenBuilds linear actuator bundle won't be as strong, but may have marginally better repeatability with an anti-backlash nut and the lubrication requirements aren't as stringent. Neither one will be accurate to +/-0.001" out of the box. The screws aren't even accurate to that, never mind the rest of the assembly. 0.003" is probably a more reasonable expectation, but sometimes you don't even get that. You need a way to calibrate it more than a simple point-A-to-point-B average. You could try looking for higher grade screws, maybe double-nut ones, on eBay that have been pulled from machines (C5 grade or higher, ground instead of rolled would be great), then grab some linear rails (or even just one fat square rail like an HGR20) and build a stage around them. The better the screw, the better your results will be out of the box, even if you have to build more of the actual actuation stage. But that's just drilling and tapping holes in aluminum, really, it's not hard. Depends on your budget, your capabilities, and your expectations.
