The best GUI around 7z.dll is the 7-zip.
PowerArchiver is the good example of useless junky crappyware. Written in Delphi, lamely protected with VMprotect (and successfully keygened by FFF), its just a candy for zero-level users.
Even on x64 system it doesn't allows to use more than 64MB dictionary for LZMA. Actually it doesn't allows to tune LZMA in any way, except poor selection of presets.
100s HalfLife.7z 192 393 829 PA Ultra
94s HalfLife.7z 192 376 058 7z Ultra
102s HalfLife.7z 184 083 003 7z d512m