No, Dell is a good mid-range brand and if you buy one of their better laptops it will do rather well by you. However, ASUS has a better reliability rating (usually on par or sometimes even better than Apple).
As for uptime, I keep my computers for at least three years and while they're my main machine they run 24/7. Granted, for a few hours every night they sleep (but not always as I tend to run big downloads or processor-intensive tasks at night) but even then I average 15+ hours a day running since I'm a web designer and use it for my gaming, music and movies (TV is pointless in a digital age, to me).
And no brand is beyond faults. Even the best-made, high-end rig will break. Make it yourself or not. Parts fail. It happens. If you go stock form a good brand the trick is how they deal with it. ASUS is a company that does it very well. Apple is king of technical support. Dell and Sony can be jerks but usually do right by you in the end. If you can get HP to do it's job it's going to take a while. Lenovo is the same. Acer and the others are just horrible. Absolutely horrible.
If you were to buy a computer based solely on how well you were supported after purchase Apple would win every time. Everyone's had a computer with a dead pixel or two, right? Little dot on the screen that won't go away. My iMac had some and they were bugging me. I had time between contracts where I could go without my main machine so I called and asked if it was covered. Yep. Now I know for a fact that just about every other PC manufacturer has a minimum dead pixel policy. Apple's minimum is 1. You have one? We'll replace the screen. I dropped it off Saturday afternoon, picked it up Monday morning. Could have hit it up Sunday evening had I paid attention.
It's also the only computer company I've ever called where the person I talked to was an actual trained tech and not someone reading a script. I can't tell you how much that matters, whether you're tech savvy or not. If you are tech savvy it means you can tell them outright what's going on, they'll ask you one or two follow-up questions and it's a done deal. If you aren't tech savvy it means you just speak plain English and they'll take it from there.
One of the reasons I love my ISP so much is because I called them and said I was "rubber-banding in BC2" and the guy knew exactly what it was. While we were waiting for my connection to reset we talked about graphics cards and good RPGs. I love a company like that.