Neither really. Ragu tastes bland to me, and Prego has way too much sugar in it. If I had to choose between the two though for something like spaghetti, I would probably go with Ragu since it's a bit runnier and closer to a home made tomato sauce made from canned crushed tomatoes. But that's being generous since everything else about Ragu I dislike, lol. I guess what I'm getting at is if I were to dress pasta lightly with some Ragu, the pasta, pasta water and a generous amount of Romano cheese would help mask the flavor a bit.
My grandparents on my moms side of the family were 100% Italian and came to the US in their 20's. Thankfully they gardened and canned vegetables for decades, up until I was a teenager when they passed away, I enjoyed many years of homemade pasta sauce on a regular basis and even helped out with some of the canning and gardening. My parents rarely ever bought the pre-made stuff in jars until we started running out of our supply from the previous season.
I don't recall their sauces ever being as thick or sweet as Prego. The only time we would have a thick sauce would be if it was a meat sauce, but the sauce itself was mainly thickened by all the shredded and ground meat in it.