Buck/Boost Converters-- What's the 'cost'?
The basic trade off between a linear (step down only, and buck and/or boost switching regulators, aside from efficiency, is lower part count, easier layout, &amp; heat vs higher part count, layout concerns, &amp; noise.

Going with a module makes the first two moot, but the third is still an issue for audio or rf or high speed data. Switching supplies can cause interference in some cases based on their switching nature. Linear regulators on the other hand, can smooth out noise. In exchange,  switching regulators are relatively cool, while linear regs heat up more as the current increases.