LED DRIVER: Buck Converters output current ripple
As the name implies, a SMPS relies on the principle of transferring energy from input to the output cyclically, and this is accomplished via a switching device and a corresponding driver. Thus, there will always be high frequency components (main switching frequency + harmonics + higher order frequency components) at the output of your power supply, but it is up to the designer to design how large their amplitude are. This is done by simply filtering the unwanted signals out. 

Now to the my suggestion:

If you are dealing with low power applications, a LDO would be the best pick, since it produces less noise (no switching). However, a SMPS would definitely be more efficient for higher power applications at the cost of requiring a bit more effort to design properly.