One advantage of the mustache bar is that it can be held closer to the ends as well as in the hooks. However, when doing so you shift your weight rearward onto the saddle too. So perhaps a sprung saddle like the Brooks Flyer is best for those bars - to avoid the repeated concussion of your butt against a saddle with little suspension built into it.

Personally, I always found the Nitto Mustache bars too wide for me to ride comfortable outside of the hooks. The forward reach of the bars is no less than riding in the drops of a drop bar. But they are bent upward, so this no longer appears so obvious. I tend to be VERY finicky about all of my handlebars and how they and the brake levers are situated, so perhaps I am a bad person to offer any advice.

I do like the look of the Jitensha flat bars very much! I have been looking for something similar with no success - Thanks for mentioning those! I have been fussing with numerous bars on an old Mixte style bike, trying to tune in just the right feel combined with the seated position desired. Like your Bridgestone it has an uncommonly long "effective" top tube... (and I have long legs and short torso). So, the original Drop bars and even Mustache bars have been rather disappointing choices in my case.

Perhaps Hiroshi's flat bar is the perfect bar for me too. It actually looks like a number of bars I've seen mounted on numerous European City bikes dating from the 50s and 60s.

Good Luck!