On pine flooring we would always recommend varnish due to the pine being softer, more porous wood, which will have better absorbency than surface protection, compared to other species. However, it also depends on how heavy the floors are used, wether the client is ready to maintain the floors 16 - 24 months (as recommended) and of course not last - personal choice, as the hardwax leaves more natural feeling of the wood.
In regards to staining - the hardwax oil offers less options and not that good durability of the colour. One colour coat is applied, followed by 1 coat of clear hardwax-oil. If maintenance schedule is not kept and colour fades out in a section of the floors, it will not be possible to be recoated / revided, which is the general benefit of the oil based products, floor sanding and refinishing may be required.
With the lacquers, the colour coat is applied onto the bear wood followed by 3 coats of durable product, which will protect the colour for the life of the sealant.
Hope the above helps. If you decide to go for Hardwax-Oil, I will recommend and include in our quote the new Osmo 2K Pure product, which offers better durability.