which most of it vs with most of it

Some examples from the web:

• Although Europe has always had its full share of varying cultures, it has also had a mainstream Christian culture or civilisation, so to speak, in which most of its people, whatever their identities, have shared.
• 'OBD-parent engine system' means an engine system that has been selected from an emission-OBD family for which most of its OBD elements of design are representative of that family.
• She's redoing any parts of the house that my father ever set foot in, which is most of it.
• Company C has one related exporting producer in the country concerned, from which it sources most of its imports.
• At the time of the granting of the aid measures, United Textiles was an undertaking which realised most of its sales to other Member States (see recital 11).
• All too often Community legislation is expressed in language which excludes most people because of its lack of clarity and complex structure.
• What the Commissioner also emphasised is that it is important to find a way to build a bridge between those countries that mainly earn their money from trade and those which have to get most of it from production.
• I would like to express my thanks and appreciation to the President of the Commission, Mr Santer, for his statement here today which is most welcome because of its optimism, its encouragement and which gives a clear demonstration of his determination.

Some examples from the web:

• - I took issue with most of it.
• Curiously, this amount is spread very unevenly over the ten years in question with most of it, more than EUR 50 million, concentrated in 2014 and 2015.