No, it's not a new Seuss book. I found an article that compared old ships to new ships and explored the differences you might encounter. It's an interesting article and found on Cruise Critic if you'd like to read the whole thing.
Basically, newer ships are bigger than older ships. I think part of that trend is because the ships are becoming the destination more than the ports of call. The large new ships are fun if you are not particularly interested in exploring some of the smaller ports where a large ship cannot go. We took a cruise on Oasis of the Seas not long after it came out and thoroughly enjoyed the week. I'm not sure we even explored all there was to offer on the ship and we plan to go again on the Oasis or one of the other mega ships.
There are also more balconies on the newer ships. We used to go for a less expensive inside room but once we stepped up to a window and then to a veranda, it was hard to go back. As the article points out however the verandas tend to be smaller than on the older ships.
Of course there's all the new stuff, electronics, entertainment specialties, even a bumper car ride on the Quantum of the Seas! Wave riders and zip lines make the slides at the pools look tame now.
Older ships are not just old buckets chugging across the waters. Cruise lines do upgrades and makeovers on their ships that help to keep the older ships looking newer and in good condition on a regular basis. The best time to sail on an older ship is soon after it's been reconditioned. New carpet, new beds, new TVs, etc. can be expected and hopefully all the charm of an older ship.
There are some things to watch out for though when choosing one over the other. We made the mistake of sailing on one of the very first voyages of a new ship a several years ago and found that most of the new electronics that were supposed to be available for cruisers enrichment didn't have all the bugs worked out. We don't book now until the new ship has been sailing a few months. And then there was the old ship we sailed that was not in the greatest of shape since it hadn't been reconditioned in a while and we were still to inexperienced to have checked it out--something our travel agent should have done. And yet there was another ship that we recognized as coming from one cruise line that had gone out of business and sold it ships. It was old but had been refurbished so nicely it was a joy to spend a week cruising in it.
Small ship? Big ship? Old ship? New ship? You decide. Do the research. Get the feedback from Cruise Critic or other cruise forums. Decide if you are cruising to see the ports or enjoy the ship more. Your cruise will be more enjoyable if you know what you want and find the best fit for you.
Ah, so many ships. So little time.