I don't put much rocket science in it - but I did both - mulitple sector short haul Europe(and Australia) and Long Haul in QR.
I have to say that short haul makes me less tired, there is always something to do, turn around is usually short, then flying again. The shift is over quickly, controllers in Europe are qualified and good. Same down under.
Long Haul instead involved far to much night flying for my taste, is long and horribly boring(IMHO, don't want to insult anybody). Was very happy when I left long haul and could start again flying narrow body short haul.
On top - if you like flying you have more chances to do that actually doing short haul.
Career - well. Depends what is important for you.
I will never do Long Haul again, ever. I just found it boring and waste of my time when on layover away from home. Others might like that kind of lifestyle.
But I was always(!) tired during my years with QR doing long haul. Sure, it can happen as well doing 4 sectors days in a row short haul. But you always recover easily, especially you do not need to recover from bloody multiple time zone flights and doing the same the next day in the other direction.