Hello there Lisa,
The kind of power supply you purchase should be matched to the application.
If your app needs low electrical noise then you usually go with a linear, but
if you need high efficiency (usually associated with higher power levels)
then you go with a switcher. If you need both, you go with a power supply
with a switching front end and linear back end, but this would be more
expensive too.
Also, if you could take a minute to describe your application (as much detail
as possible) it would make it possible for people here to make a much better
recommendation.