base2 

I rarely weigh-in on threads like this, but here goes: The flat bar with aero clip-ons is a really good idea. Flat bars just plain suck if they are to be used for any length of time outside their mountainbike domain. The aero clip-ons provide an elbow biased fit that completely eliminates any wrist, palm, and nerve derived pain in the forearms, shoulder and neck. This pain happens because the wrists are bent at an unnatural angle and carry a bunch of weight that should be bourn by the riders core. The unnatural angle also kicks out the riders elbows forcing the neck muscles essentially double duty to support the lats & traps so the triceps can hold the riders torso upright.

Don't get me wrong. Flat bars are fantastic for standing and leveraging around a bike for short rides in wildly varying terrain. But for moderate to long-ish distance on flat-ish terrain for medium to long times, the neutral wrist position is the way to go. On road bikes, the drop bar is the most common, however it is used. On a city/utility bike a bar with a lot of sweep like a Soma Sparrow, or a North road, or a touring bar is the better choice. The decision between "road" and "swept back" ought to be determined by the distance and speed intended.

Dutch style utility bikes really top out at about 5-8miles at about 12-14mph. For this, there is no substitute. Swept back bars and upright posture sitting on a seat are the absolute best for this.

For greater distance and speed than the Dutch, road handlebars on a bike that uses a saddle is the solution. The key for either is the neutral hand/wrist position that either shifts the weight back to the saddle for ease of low effort use or the core muscle engagement for performance. Either way the result is the same: To keep the weight off the hands and let the arms fall in a generally straight relaxed line from shoulder to contact point.

Flat bars don't offer any of this, nor are they meant to. Mountainbikes are for mountains. It is unfortunate; the influence mountainbikes have in the American marketplace essentially crowding out the more utilitarian and practical uses that other bikes are better suited. Americans are anything other than realistic when assessing their actual needs. Utility bikes like the English 3 speed are just too humble to appeal broadly to American consumers. (Though this is beginning to change thanks to infrastructure adoption. Practical bike companies like Public, Linus, Pashley, Momentum, Gazzelle, and various e-bikes to cover Americas poor urban planning and excessive car culture derived distances with roadbike like speed at recreational utility effort are gaining in popularity.)

Due to the aspirational "can do all, must do all," nature of American consumers based on "adventure" or "pioneering spirit" or whatever you wish to call it, ill-suited flat bar mountainbikes often get bought based on the idea of recreational activity, dominating mountain trails, or the allure of practicality. But sadly, those bikes often get shoe-horned and force-fit into ordinary utilitarian uses that Dutch bikes or drop bars satisfy better. The truth is most flat bar mountain bikes never even see a dirt path in their entire existence or are rode for more than a dozen miles or so around a campground a couple of times and then get dumped or discarded as uncomfortable or impractical. Then we get discussions about: "Why handlebars with neutral hand positions?" ...If only the OP titled the thread with those words instead.

FWIW: The OP needs a Dutch bike. Every "mountainbike" that is used for utility like commuting or groceries gets turned into a Dutch bike...eventually.