appcheck and kaspersky are very stable
appcheck > kaspersky: zero-day ransomwares. appcheck can revert most encrypted files, sometimes, it misses but files can be found in the backup folder
kaspersky (online only) > appcheck: a few day old ransomwares, MBR ransomwares
kaspersky has KSN (cloud) which can detect many ransomwares instantly. It has system watcher (a weaker version of the actual kaspersky suits) but it's much less effective than appcheck as malware hub tests proved it
another solution is 360 folder protector. it's not an antiransomware tool but it can backup files before any change applied. it can be used with other other tools in case antiransomware tools and AVs fail to protect, files will be safe (backed up) regardless of the infection
I can recommend kaspersky antiransomware + qihoo 360 folder protector = free. this combo is also great and your files will be aafe in most cases, better than appcheck free alone
appcheck pro can do everything: backup, protect MBR if you are willing to try and pay
360 folder protector is good if you know where to recover the files but not good for users friends who don't know anything about PC + you can't help them