I'm a big fan of IKB, but I think he was a good engineer, but a superlative project manager. The latter was his real skill.
For a superlative technical engineer, I think my money would be on Barnes Wallis - who also was a brilliant manager and networker, the latter being at the root of so many of his successes.
When he designed R100, he managed 11 discrete parts in the entire 72ft/33ft framework (50 if you separate by material gauge). You'd struggle nowadays to find many aeroplanes with that few discrete parts in a door!
Which is not to denegrate Hooker. We were privileged in Britain to have a group of incredible engineering geniuses at that time: Mitchell, Hooker, Camm, Wallis, Shilling.... Comparing them is an interesting intellectual exercise, but the reality is that in their own sub-fields, each was unsurpassed.
G