My advice is DO NOT got cheap. Get the best you can afford with the most memory available.
That said, I run my company on a Dell XPS 14Z and LOVE it. I had a Dell XPS M1210 for 4 years, still working and sits here at my desk where I go back and follow up on things from time to time. I chose not to put everything that was on the 1210 on the 14Z because I need the faster processor and more memory for my Quickbooks, etc. I purchased both of mine directly from Dell. My new one was less than $2000 including a top warranty and all the software I needed.
Hubby has a Dell from Best Buy and it works well for him. I forget the model but it has a top warranty as well. He runs our company on that computer. It is lightweight as well as it does not have a disc drive.. that is separate. We paid less than $1200 for his set up.
Daughter, now 17, had a Dell Latitude for 4 yrs. She had a lot of music, etc along with programs she used for school projects. At the time, we spent about $2000 on her Dell.
In August, we upgraded daughter's computer to a MacBook Pro. She LOVES this computer and swears it is the best thing ever. She has a lot of music, watches movies, runs office and power point. Her classes require a lot of power point presentations and she is in 11th grade. We got it at Best Buy with a top of the line warranty and we spent more than $2200 on her set up.
I strongly considered a MacBook Pro for myself when I upgraded but it had some things that were not compatible with my Quickbooks and I MUST have something that runs perfectly for my business. I chose to stay with Dell ( I LOVE Dell) because it is easier for my payroll, reporting and contact with my accounting team and IRS reporting.
SO, If you can afford it... I would go either with the MacBook Pro or Dell.