Maybe nothing. The high power should have a higher power output for more range, but the high gain should have a better antenna for more range.
Thank you for the reply.. The store I bought the adapter can't explain this difference, although these two types differ very much in price. I now think that they don't even know the High-power one can do TRANSMITTING also (I also know that just now
). They sell both as a device only for RECEIVING signal ...