I have vague - but only vague unless I go do some checking - recollection of fuel gauging accuracy being quoted as a proportion of total/max fuel, not of current fuel. So it can be pretty poor at low fuel states.
I also seem to think that fuel flow accuracy suffers similar problems at low fuel flow rates.
So either might be good for a heavy aircraft, but a light one burning little gas will be a pest whichever means is adopted.