To me, it looks just fine for stability. I have several similar, tall
2-step stools (made with scrap lumber, not nice pieces of furniture) I
use in the shop.
Consider what you would be using the stool for.
In my case, a stool as that is not for assisting in handling large
pieces of lumber or other heavy objects from above. It's for reaching
small items, which can be handled comfortably. Trying to handle
larger, heavy objects, to me, might be a more cautious effort on that
2-step stool.... or just about any small stool/ladder/5 gallon bucket
with an awkward or not-so-normal step. Common sense would dictate
what is safe or best.
The steps' rise does seem to be a bit tall, though. I can see it
being used in a pantry setting. I would prefer the 3 stepper for a
library setting. Asthetically, it doesn't look as desirable as the 3
stepper for an in-home setting. I would not make a fairly nice stool,
as that, for use in the shop.
For in-home use, I vote for the 3 stepper. For a 2 stepper, I would
a) reduce the rise of the steps or b) expand the base (my least likely