I use a custom built PC for my desktop and a Dell Inspiron for my laptop. I do heavy 3D work, so most of the time I'm on my desktop since the processor is built for multitasking and the video card has tons of RAM.
For PCs, it's almost always better to not get the latest hardware since the version before will cost a fraction of the top price and give you just about the same performance. So the major question is, what will you be using it for? Graphic work? Word Processing and internet browsing? High end gaming?