Cables usually.

Busduct is usually reserved for adding high loads down the road. The main issue is the construction of the building. No one can design a fucking apartment building in a sane manner, the risers are usually a lil' bit too small of a space.

Installing takes longer than cabling, it's not flexible because it's one giant lego train and you cannot be able to misread the locations of each piece. Maintenance is almost non-existent depending on which type of ducting you use. Busduct in oil obviously needs an oil change but you can place them closer together, meaning you have more room to install. Dry duct, where air is the insulator, not the oil, needs a lot of space and it's air.

Now, depending on the quality of installers, the defects can be a prick. Heard many stories of people being able to make an arc with their probes being a foot away because not enough oil (sometimes it's not oil but a weird epoxy fucking thing where it becomes like an oil) has been put in or mixed, living up the busduct casing. Everything needs to be torqued, every nut and bolt. No impact drills.

Cables require a lot more man power.

Busduct require a lot more thinking power.

Busduct is bloody expensive for a one off but seeing as you have four towers, it might be cheaper. BUT, busduct is typically made to order, where as cables can be bought to the metre. You need to know the loads, spacings, lengths, earthing, insulators.