Reduce WordPress plugin spam blockers where possible by using a webhost that provides spam blocker functionally at the server level so that it gets nowhere near your secure WordPress website.
Since this post was originally posted, the SI CAPTCHA Anti-Spam WordPress Plugin has been removed from the WordPress repository of plugins.
I have used the same managed secure WordPress webhost since January 2015. They have implemented additional spam blocker functionally at the server level. This means that similar spam blocker functionally provided by WordPress plugin spam blockers is now not required.
This saves an amount of time installing, activating and maintaining these different WordPress Plugin Spam Blockers at my end. It also means that I do not have to spend time learning how to use these different WordPress Plugin Spam Blockers. Not all were simple installs, some required a time investment in order to actually implement. Others were simple: install, activate and forget. Even so, as WordPress Plugins, they also tended to be updated on a regular basis. And if they did not need updating, it tended to raise questions at the back of my mind as spammers are always trying new things which from time to time would require updating.
Now that my webhost provides this spam blocker functionally at the server level, I do not need to install and activate WordPress Plugin Spam Blockers.
My webhost also has additional functionally which includes several layers of security that shields websites and helps keep them secure.
This website security includes hacking, malware and bot-net attack protection.
Whatever overall solution your secure WordPress hosting solution has, it had better include several different layers of security. Having several layers of security makes a lot of sense.
The website security package needs to at least cover hacking, malware and bot-net attack protection. If the website security package includes protections at the server level, it may mean that there is no requirement to install a number of WordPress plugins that provide duplicate functionally.
For me now there is no need to install and activate the Akismet WordPress plugin or the SI Captcha anti-spam WordPress plugin or the WP-Spamshield WordPress plugin as my webhost provides similar spam blocker functionally at the server level.
I now use zero WordPress plugin spam blockers as my webhost already provides similar functionally at the server level.