Most high-frequency (HF) designs emulate smooth 60-cycle waves from 40,000 or 50,000 spike bits and filter smooth the result, cheap to manufacture and small and lightweight to ship, store and display. HF units don't have much 'surge' or 100% continuous duty ability unless seriously overbuilt with price factor to match.
The LF units physically weigh 3, 5, 7 times that of the HF units due to large transformers and heavy copper storing potential magnetically versus firing a string of transistors another 1000 times; LF usually* will throw their label ratings all day long without complaint, with large surge capacity, and having the slower switching speed are less vulnerable to spurious timing issues that cause chain-reaction meltdowns in HF units, slower control signals means less radio-frequency noise pollution too.
Cheaper*
China eBay LF units have vastly improved the last few years, think low idle current and high overall efficiency but yes, there are AIMs brand units too that have all the charger and AC changeover gimmicks for 3x or 4x more money. The China units aren't perfect but are made to self-service, control boards and replacement parts cheap and sold direct. Think buying three of four units for the price of one US retail unit, and jumpering in home-built remote functions, linked vendor has real good feedback for selling 1000's of these.
AIMs LF units warranty is only a year and user pays shipping. Sensata Dimensions LF is a pricey brand, there are some ebay deals on used ones.
