You can see from the chart of digital piano specifications that it's not unusual for different models from the same manufacturer to have different warranty terms. It would be tempting to attribute this to differences in quality, but most often it's based on differences in anticipated use (home vs. commercial), and on marketing decisions for a given product segment. Unlike some warranties for acoustic pianos, I'm aware of no digital piano warranty that is transferable to a subsequent owner.
There are many decisions to be made when selecting a piano, digital or acoustic. But in the end, there is no substitute for playing and listening for yourself. The best anyone else can do is tell you what he or she would buy. But unless that person's requirements exactly match your own, all you'll end up with is a piano that's perfect for someone else.
Go out and try everything you can get your hands on — and enjoy the process!
For more information
If, after reading the articles in Piano Buyer, you still have questions about buying a digital piano, I recommend visiting the Digital Pianos — Synths & Keyboards Forum on Piano World (www.pianoworld.com), the premiere website for everything related to pianos and pianists. The helpful folks there have a wealth of knowledge and advice they are happy to share.