I think the main difference looking at it from a Christian perspective is Catholic's worship in a more cerimonial and ornimental way.
Catholics have baptism, communions, rosarys, crossing them selves before going into prayer, confirmation, and they say the Hail Mary and Our Father prayers a lot. I've been to masses at a few different places and I can always expect the same things. The singing, prayers, the readings, the sermon, the communion, the exchange of peace (i like this part!)... etc.
Christians just basically rely on their faith to worship. We do get baptised (I did 3 years ago), but other than that there are no big religious ceremonies. Church basically consists of singing gospels (or in high school worship we sometimes sing contemporary worship songs), praying and the sermon. It's just more basic, and though I have no problem with the way Catholics do it, I prefer it that way. I'm strong in my faith, and I don't think I need anything else. I'm more spiritual then religious (by the book) though, so I guess that's why I like it.