PC Toledo

UPX strengths in a nutshell:

secure: as UPX is documented Open Source since many years any relevant Security/Antivirus software is able to peek inside UPX compressed apps to verify them
excellent compression ratio: typically compresses better than Zip, use UPX to decrease the size of your distribution!
very fast decompression: more than 500 MB/sec on any reasonably modern machine
no memory overhead for your compressed executables because of in-place decompression
safe: you can list, test and unpack your executables. Also, a checksum of both the compressed and uncompressed file is maintained internally.
universal: UPX can pack a number of executable formats, including Windows programs and DLLs, macOS apps and Linux executables
portable: UPX is written in portable endian-neutral C++
extendable: because of the class layout it's very easy to add new executable formats or new compression algorithms
free: UPX is distributed with full source code under the terms of the GNU General Public License v2+; either under the pure GPLv2+, or (at your option) under the GPLv+2 with special exceptions and restrictions granting the free usage for all binaries including commercial programs as stated in the UPX License Agreement

Pelo que diz no site, não deveria dar problemas se segurança (como ser considerado um risco por ser confundido com virus), pois por ser de código aberto, relevantes antivirus poderiam vasculhar dentro para verificar livremente. Creio que alguns antivirus analisam por meio de algum algorítimo heurístico e acabam associando alguma combinação de código comprimida que cause eles a considerar como risco, mas esperamos que isso vá reduzindo à medida que vão ficando mais "inteligentes" (ou não...)

Diz que a velocidade de descompressão é de 500MB/s, muito rápido, não será perceptível. Vale a pena pela vantagem de reduzir o tamanho do EXE.

upx sistema.exe --compress-exports=0 --strip-relocs=0 --compress-resources=0 --force

upx sistema.exe --force