It is recomended to make your own PC but often you can get better deals in prebuilt PC's cause computer shops do tend to give a certain discount on prebuilt systems.
You will want to check every component that is in prebuilt system, and if they suit you and you can't get that kind of deal for self building then you should go for it.
But be carefull. Lot of cheaper (not all) prebuilds have at least one underrated (cheap) component that is not obvious. 99% of time PSU is that cheap component. If that is true then don't buy it, go for your own.
Best regards