 Switch mode power offers many advantages over the older technology used in linear power supplies. Switch mode power supplies are smaller and lighter as they don't require the large heat sinks and bulky transformers found in linear supplies. They're also more efficient. Linear supplies waste a lot of energy as heat, topping off at around 30 to 40 percent efficiency. In contrast, there are switching supplies out there boasting 96 percent efficiency. Pretty much every wall supply you see nowadays uses switch mode power. But there is a downside. Switching supplies can introduce noise into your circuit, both conducted and radiated. Proper RF shielding and output filters can do a lot to help reduce that switch mode noise. But if your circuit is particularly sensitive to fluctuations, you're best off using linear power. Or the portable low noise option. A battery.