I want to know which one would be cheaper for a desktop to build one or buy one.

well, building your own means you don't have the added cost of labour for someone else to build it. and in building one yourself you get exactly what you want without extra bits you'll never use.

The price difference isn't much these days. However, if you have specific desires -- video editing, gaming, etc. -- you get to pick the components best suited to your needs, rather than settling for what the OEM may offer.

Computers used to be a lot easier to build. The HSF for my 486 weighed only a few grams and was made entirely out of plastic. Now you need some sort of gigantic metal monstrosity to keep CPUs cool.

 

It depends what matters to you. For a system with a good thermal and acoustic profile you're much better off going OEM. Unless you're willing to sink even more money into making a quiet system or one which does an excellent job of cooling, chances are any box you're going to build yourself will be quite loud and run hot.

I think as long as you're going to have time to keep up with your system, building is definitely the way to go, and it will run much more efficiently in most cases - however, if you just want something that'll do what it's told and get some help when it doesn't, definitely go with an OEM system, they're getting better

the benefit of going OEM may also include free tech support and warrunty to fix big problems you can't handle yourself.

 

Even if the machine is more expensive, you could wind up saving money if you don't have to pay for replacement parts.

 

(Although upgrading may void the warrunty?)

It depends on how involved you want to be in the machine. If you just want something that works, and works reliably, then go OEM

 

I would only recommend building if you want the experience of building it, or you want a custom/personalized machine. And in both of those cases, it wouldn't be worth it unless you are building a high end machine.

 

Since you are asking about money, you might be best served by just buying a machine. You can't discount the very significant time investment that you will need to make when you build a machine.