Congratulations on chalking up that significant anniversary, well done !!One difference is that an engagement ring - a gold ring with a precious stone, especially a diamond - won't wear out - unlike a watch. I wouldn't buy a watch instead of a ring. I have no doubt my wife prefers her ring to any watch. It still looks like it did when she first wore it, over 40 years ago. Under a loupe, there might be a few scratches, but that's all.