I think it would be best if you could expand on where you intend to fit the items. In general it would be person choice which type of light you used, but when it comes to safety with areas of the bathroom the ELV (extra low voltage) would be a safer option.
They will both require ventilation both fitting and transformers, and likely they will both require to be fire rated, possible rated against moisture ingress to. Standard junction boxes can only be used if they are easily accessible for inspection, testing and any repair work. There are methods of jointing cables that don't require junction boxes, but normally specialised tools and knowledge are required to make these joints. Unless you use maintenance free boxes. Also you will find that often installation instruction state no earth required, but this does contravene the electrical wiring regulations, so suggestions are that you still keep CPC/Earth conductor continuous, this will also help when testing for r1+r2, Zs and faults.
I'm looking to install them in the hallway (plasterboard ceiling) There is currently a pendant and the property is a new build. The hall is next to a bathroom in which are currently installed downlights - so I assume at this point the hall ceiling is of a similar construction. Although I am not planning any work in the bathroom.
240v would not require transformers though, right? Do these not just function as regular lights? (am not sure)
No problem using maintenance free boxes or earthing - good advice thanks.
240V GU10s don't require transformers. They will function as a normal lights, off normal switches. I would do a little investigation prior to purchasing lights though: The depth in the ceiling void will need to be measured, as the fitting will require a gap between them and the floor above, this will vary on type/manufacture of product, so best check now. Also joist spacing in the ceiling void can make it difficult to space and line the lights, so aesthetically pleasing. Also avoidance of close fitting to combustible materials and thermal insulation and make sure they are fire rated. There are also regulations concerning where a joist can be holed, this can be found in approved document part A of building regulations.
Ok - so they do not actually need to be bonded to the light casing..? Just terminated at the fitting (in the same way as for a plastic light switch e.g. where the earth is terminated in a connector strip but just left in the back box)
Forgive me for saying so (am not sure I understand the principle) but seems a bit odd - does that not just mean an extra run for the cable for no actual benefit i.e. nothing is actually earthed, surely..?
There are a few reason behind it, BS7671 (wiring regulations) actual state that a CPC (aka earth cable in this case) must be terminated. From BS7671: A circuit supplying one or more items of class II equipment, shall have a CPC run to and terminated at each point in the wiring and at each accessory.
So even though they class II double insulated, they still require a CPC, it does not and must be connected to the metal fitting, in a connection block, safely within enclosure will do. Also there are added advantages, when it comes to testing and fault finding, and without a continuity of the CPC to the final fitting, you cannot take a Zs reading, which is also a requirment. Then if you ever replaced this fittings and fitted lights that required the CPC to connected to it, they are there.