How so? The altimeter "tape" does scroll in the direction and at the rate that the aircraft is climbing/descending, in much the same way as the old "steam gauges" rotated/unwound.
Dozy,
You need to hand fly on instruments using both systems, then tell us which you prefer, but first you will have to develop and perfect a scan.
Remember? The crew of AF447 was tasked to suddenly take control and hand fly their aircraft. They failed this elementary task. One of the first things they lost control of was maintaining altitude.
Obviously, both systems of altitude display work, but which works better from the human standpoint?
The scrolling tape is essentially a rate signal and is easily picked up, but the actual altitude being traversed requires the eye to focus on the numbers, which then must be mentally interpreted as an altitude differential.
The counter pointer type display is more nearly an actual altitude error signal and for small errors, it is easy to pick out the amount of error by the angle of the 1000' needle as stated by roulishollandais. For rapid climbs/descents, the rapidly rotating 1000' needle draws attention to itself and is unmistakable.