My 9 mm Browning Hi Power is juuust right.
The all steel Browning design is classic, but the 9mm has evolved more than most other rounds. Some of the newer 9s, like glocks & even beretta give the old hi power a good run for its money. Toss in the XD, CZ, Sig, & HK, and the field is pretty crowded. Granted, one could argue that the browning design formed the foundation for all of the others, which were primarily just tweaks on perfection.
But considering the tweaks, i've got to go with the glock as the 'perfect' match for the 9mm cartridge, now. IMO, it has enough improvements to warrant taking the crown from the older design. the g-17 might be the most carried LEO piece in the world, & only after a short time, historically speaking. And the g-19 is almost the perfect balance of power, capacity, weight, balance, & concealability.
I give credit where it is due, & JMB is still the reigning king of firearm design & perfection. Nobody comes close to him in this race, even Mikhail Kalashnikov's AK-47, the most popular warfare rifle in human history. Browning beats him with variety, but MK wins with specialization & sheer volume.
But, since this is an opinion poll, with the criteria being 'optimal', a not very clearly defined standard, opinions will vary a lot, & personal preference can trump volume or historical significance.