I guess you could make the analogy to older vs. newer cars. The older cars have classic lines and are all made of heavy steel. The newer cars are made of some lightweight composites and the lines are... ummm... modern... for lack of a better word. I suppose most improvements are in the safety department. New cars have seat belts, air bags, crush zones, etc... and modern guns have improved safetys, key locks, magazine disconnects, etc.
Then there are "user convenience" items, such as night sights, lights and lasers, tactile grips, ambidextrous safetys, etc., and guns now come in colors.
But I gotta tell ya... I love the classic looks of an old Mercury or an Oldsmobile 455 Rocket. I'm kinda nostalgic that way, and I guess that's why one of my favorites is my Springfield Armory 1911-A1, a classic design with a few modernizations.