It depends on the situation. Here are some things to consider:
If you're just looking for a place to sit, then buying ready-made furniture is probably your best bet. But if you want something specific—whether it's a king size bed that is exactly the right height for you, or a desk that fits perfectly in your office—then customizing is the way to go.
If you have a lot of money to spend on new home furniture, then buying customized pieces can be an excellent investment. This way, you'll get exactly what you want and won't have to worry about replacing any of it later on down the road. If money is tight, however, then going with pre-built options may be more affordable for now—and then you can customize them later on when your budget allows it!