Is it more stressful to be a leader or a staff officer/NCO?

Being the leader, who is then put in a Staff position...is tougher then either.
Had the stress of leadership, then moved to a staff position "because you know what its like be waiting on resources, info, help"
Now that Infantry leader that has led patrols is the support platoon PSG, "to fix things and get it done" or the Battle NCO in the TOC "Because we have to get this right of lots die" or the S-1 PAC "Because that idiot in there now is killing morel and confidence in the unit with all the crap he is screwing up effecting spouses at home"
All reason I have seen mid and senior NCOS moved from a successful role as a team leader, sqd leader or PSG, to a staff position because the very smart commanders knew, mediocre NCO as a SQD leader means a somewhat less effective platoon...mediocre NCO on the radios and tracking board in the TOC means the entire battalion is at risk anytime an element is outside the wire.

Having bounced back and forth, in Staff positions, it seemed I got all of the stress and none of the glory. Very little job satisfaction, and it seemed a daily grind of reports that effectively moved paper from one in basket on my desk to another in basket on another desk.
Whatever stress I experienced in leadership positions was always offset with the feeling of accomplishing something with my Soldiers.

Leaders, that is commanders, may have to make decisions that could, and sometimes do, get people under their command killed. I was a staff officer and Army Civilian in a staff-officer type position for over 10 years. No decision I made or order I wrote or edited directly endangered the lives of military members or civilian employees. The people with "commander" below their name were ultimately responsible for those orders and the associated successes or failures. My job was to make sure the orders or directives were written clearly and coordinated as completely as possible, within time constraints, to set up the subordinate units for success. The staff job often involved lots of "paper work" and maybe some long hours, but not the heavy responsibility of command. That's why the Services tend to promote people with command experience.

Having done both, though not all in the military, I believe stress reactions to be the same but the stressors are different.

I voted same but that isn't right either. They both have their stresses and every person handles each office differently. I would also say that the leadership and peers you are working with can either reduce or exacerbate the stress in each position. During my time I worked in both, within my MOS and at BN and above positions. The people I had around me made me succeed as all I did was my job and duty. I would reiterate that I believe they both can be extremely stressful but both can also be very rewarding.
Excellent question, BTW.

Being an NCO you not only give orders and follow up on those orders but one of the most important aspect of being an NCO is to be a positive role model as well as a mentor!

That depends on what problems present themselves today.

Stress is reaction to the combination of environment and ability. You may not always control the former, but the latter is largely in your hands. Leaders are not necessarily commanders and staff members are sometimes leaders. What you really want to ask yourself is this: If I am given the responsibility and authority to act, am I truly ABLE to do so? If the honest answer is "no" then you have the moral responsibility to pass that empowerment to someone who can...especially if it could lead to fellow warrior's demise. People in combat and staff positions are important to each other...they are not mutually exclusive. The supply sergeant (staff member) could certainly impact the soldier if they don't (or can't) do their job. If shipments don't arrive, there's your stress. If the platoon sergeant can't get rations from supply, there's your stress. Both are victims of their environment (lack of materiel flow) and both experience stress. I recommend we lose the "leader vs. staff" differentiation mindset...instead let's embrace the "we" and the "us" words that will help reduce stress for everyone.

Staff, justification of others ideas is a pain

I absolutely loved working as the schools NCOIC. I was still a leader of an NCO and a few Soldiers, but it was a lot less stressful than working in the building and being a leader.