And some people just like shiny bullets to go with mirror shiny brass.
I can't prove it "scientifically" but I strongly suspect ^^THIS^^ is the real reason people who prefer plated, prefer plated.
It's all about the application for me. Paints, enamels, waxes, grease and/or plasticine bonded coatings perform a similar function to a lubricant: place a friction diminishing film barrier between the lead and the barrel to prevent hot gases from melting lead into the grooves and allow the bullet to travel the bore at higher velocities with less pressure. Plating - copper or nickel - performs a similar function but is not a lubricant, does not diminish friction appreciably, and is not as hard as a jacket, but can be (typically is) harder than a plastic, enamel or paint coating; it is a stronger, more nearly heat resistant material which the hot gases cannot melt as easily or as quickly, and are better at shielding heat from the lead cores they're bonded to. Jackets - steel, nickel, copper, brass, etc. - may or may not diminish friction but are considerably harder and more nearly heat resistant than plating or coatings. As much as people complain about waxes and greases, they are coatings like any other, have been around a very long time, and generally do a fine job of protecting the bore and the lead bullet, when applied correctly.
Bullet fit, powder choice, barrel length, primer choice, caliber... lots of factors go into making the decision what to load and how to load it.
If you're loading hot, high-pressure, under-size, and high friction, jacketed or plated might be the best choice. For lower-pressure with powders that don't generate as much heat, and properly sized bullets that seal well with less barrel friction, a coating - wax, paint, plastic, what-have-you - may be better. Always ask your doctor before choosing the coating that's best for you... YMMV. No deposits, No returns.