I've always mixed my own mortar for re pointing, using one of the NHBC recommended mixes.
1/0.5/4.5 OPC/lime/sand, or 1/3.5 OPC/sand + added plasticiser or 1/3 masonry cement/sand. These are good for harder bricks.
These mixes have always done well in our climate, but yours may vary if it's a lot different.
Generally speaking strong cement mixes are not recommended for old softer brickwork, but are sometimes used in very exposed conditons.
On really old decorative stacks a hydraulic lime mix would be better.
There isn't really one mix that applies to all jobs, it's a question of picking the right one for a particular stack.