Are there any modern tradeoffs that come with designing more efficient DC-DC switching power converters?
The high edge rates that high efficiency high frequency DC-DC converters usually require can potentially generate harmonic EMI/RFI across a vast range of EM spectrum (multiple HF shortwave bands and up), even if within legal (U.S. FCC, Part 15) RF limits.  Good EMI/RFI filtering on the output and shielding of both the converter and the input feed cabling, both in design, and across component tolerances over a large production run can add to product cost.  Mechanical stress, aging, and connection oxidation can allow an increase in any emitted EMI over time.