New suspension fork - how much should I care for locking on the handlebar?
Any fork lockout per-se is a sign of suspension design limitations, one would argue. An ideal suspension system would tune the closed/open states by its own, and there are attempts to achieve that (Specialized Brain, Magura Elect etc.).
Rider's mental energy spent on making lock/unlock decisions translates to lost joy of the ride. Unless every second counts, i.e. one is racing against the clock, and needs all the efficiency all the time.
An always open suspension fork will not turn a ride over a smooth surface into suffering. A little loss, not unlikely unmeasurable, of pedaling efficiency will happen, and that is it.
Similarly, a proper fork, even when locked, will have a blow out valve to open up by itself when a rider encounters a bumpy segment. However, this situation is more dangerous than leaving the fork open all the time. It is better to foresee the need to open the suspension than to rely it to happen on its own.
The difference between lockout control placements manifests itself in how much time the cyclist needs to spend to switch it. When commuting, touring or leisure riding, lost seconds to slow down, find a knob on the fork and turn it are really not that critical. When racing, slowness is of course unacceptable and a lockout placed on the handlebar is preferable. Not that it does not have its negatives: 1. One more knob on the handlebars to mess with; 2. One more cable and housing to periodically replace; 3. Additional weight of additional components.