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Waist of a good back ruining it by needlessly lugging a 110v step down tranny about to drill a few holes to put up shelves.
It's not even a legal requirement; on all sites you CAN use a tested RCD with a 240v supply. Most big sites will switch off the 240v supply until handover though as it's too much of a headache to check that the usual crowd of muck savages aren't getting "creative" to bypass an RCD that keeps tripping.
If you are running a chopsaw or table saw onsite you NEED to have a mains powered unit if it's going to see anything more than light use - on big sites the battery charging station could be a 10 minute walk away. Also battery table and chopsaws are no where near as powerful as the mains counterparts so will struggle with tricky timber or difficult cuts.
Myself and most of the other guys.i work with tend to have 3 of each tool (this list doesn't include small sds drills, comvi drills or impact drivers but does include the likes of drywall screwguns): one battery one for occasional use pottering around site ticking off jobs on a snagging list, 240v mains powered units for general domestic work, 110v for big sites. Obviously if you only do domestic you won't have many 110v tools and if you only do commercial you won't have any 240v tools for work.
Trades that are only on site for a limited time and then go will rely on battery units much more than any other trades because they don't have to worry about PAT testing as much or going through lengthy PAT test records with the PCs health and safety man.