It was
noted in the movie that Ultron is limited by a fixation on trying to copy and improve the human form specifically, even when according to Stark, taking a nonhumanoid form could have been more efficient. If the Vision body is a glass cannon, it'd largely be the result of Ultron prioritizing having his ideal form be as humanlike as possible.
That said,
Stark did believe that the Vision body would be more powerful than any, possibly all, of the Avengers at the time (which the What If? episode supports), and the Phase Three, Captain America: Civil War novel gives Vision a similar statement:
And even without ever getting to use that body himself, Ultron is still described by the Age of Ultron artbook as the greatest threat any of the Avengers had faced up to that point, presumably indicating that Ultimate Ultron should be more powerful than the likes of Kurse: