I DEFINITELY recommend getting a Macbook. I got mine back in June 2008, and I have had ZERO problems with it. Macbooks are great because you never have to deal with Viruses, the connection to the Internet is always fast (especially if you buy your own Rowder), and Macbooks rarely crash on you.
Again, I've had mine for two years, and have lugged it back and forth on trips, commuting to school, on planes, and I've had no problems. It's never crashed on me, even though in the past I probably have fried the battery because I charge it all the time (a piece of advice on the side to you, a prospective Macbook user: don't over-charge your laptop, that is a no-no). Still, I've even done that and it still works great. Plus, I've downloaded a few systems onto it which could have slowed down a DELL, but my Macbook is still super-speedy. However, again, if you do get a Macbook, I recommend buying your own Rowder for it if you do not already have one.
I had used DELL's my whole life until I got my Macbook, (I used mostly the DELL home computer at my house), and while navigating through the new system will be a bit different, you will get used to it right away. Macs are not priced better because they are "cool", they last very long and they are reliable computers.
Tell your dad: this is coming from a Dell user who switched to a Macbook almost two years ago, and so far, I have only glorious thing to say about my trusty Macbook. It is expensive, yes, but with a student discount, you can get 100 bucks shaved off the price. That doesn't help a LOT, but it's still something. Plus, tell your dad that instead of buying 3 Dell laptops over the next few years again (whoa!), your Macbook will be considered an investment that will last you a long time.
And a sidenote to you: if your dad does get you the Macbook, which I really hope he will, it is up to you to take care of it. I recommend buying a case for it so when you need to carry it in your bag, it will be kept safe. And be careful if you do homework on your bed, so that you don't drop it or spill anything on it.
I've spilled a bit of water, and even once, Iced Tea on my Macbook, and it still works great.
Hope this helps! Good luck, and if you do get it, treat it well :)