What are some alternatives?
When comparing GPGTools and KGpg, you can also consider the following products
Kleopatra - Kleopatra is a certificate manager and GUI for GnuPG.
GnuPG - GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).
GPG Suite - Use GPG Suite to encrypt, decrypt, sign and verify files or messages.
GPG4Win - GPG4Win is an encryption program for files and emails. The program encrypts emails and files so that they can only be read by those intended to receive them.
Autocrypt - Convenient End-to-End Encryption for E-Mail
PGP Tool - PGPTool allows you to encrypt and decrypt files. It's free and easy to use.