Well, sure, sometimes a brand computer such as HP or Dell will be more stable as for components and durability, but you will get a much slower performance computer for more money.
For example, i need to buy a computer for my game reviews, as the ones i have now can't run newer games with good settings, some at all. I will definitely be building one on my own, because i have already built a computer configuration for around 470 USD(without monitor/keyboard and other external components that i already have) that outperforms a dell priced at 700-800 USD, so you understand why it is important for me, i need great performance, and i prefer not to spend too much money on it.
Sometimes it is luck if your configuration is a perfect match between motherboard, graphic adapter and cpu or not, but... if you get it right, you can get a stable, good, high performance PC for a good value.
But, you said you might not completely be interested in the performances of the computer, so, the question you should ask yourself is what will you do on your computer?
What are you going to be using this computer for? Will you be using office and image editing software? Maybe you want to play the newest games out there?
If you're doing work that requires better stability and less performance, then you should go with a brand PC.
If you want to play the newest games, then it's always best to build one for yourself, because it is cheaper.
Just remember, it mostly depends on your needs, and line of work. Most manufacturers put fairly good CPU's in brand computers, but not so great graphic adapters, meaning that all sort of statistical and data work will be done with good stability on such computers, but playing the newest games, is, as i repeated a couple of times, quite... impossible.