Formspammertrap for comments (FST-C) was the initial implementation of the techniques used in the main (non-WP) FormSpammerTrap (FST) (available free at https://www.FormSpammerTrap.com ) . I used the techniques in FST to allow FST-capabilities in a WP comment form.
FST-C has additional features that allow you to customize the comment form area – heading, fields, text before/after the form, etc. It is fairly effective, but the latest FST techniques aren’t in FST-C. I probably should add those latest techniques.
FST also has lots of customization features that are built for contact forms, rather than just for comments.
But the standalone FST has instructions on how to make a template page using FST. That requires a bit of template-creation knowledge, but the instructions are in the FST files you get from the site.
The Block Comment Spam Bots (BCSB) plugin is built to block spammers from using manual ‘posting’ of the comment form via something like CURL. It’s a simpler version of FST-C without the additional features of FST-C. BCSB is very effective in blocking automated CURL-like submissions to your contact form. Maybe even more effective than FST-C.
BCSB also puts less ‘load’ on the database, as it does it’s thing before writing to the database. So you don’t even see the blocked comments in the database as blocked. They just never get to the database.
As to which to use? I use FST-C along with BCSB (even though FST-C is not as current as FST). Together they are quite effective at blocking bot submissions to your comment form. I also use templates I create using FST for ‘contact me’ forms. That is quite effective in blocking contact form spam.
Hope this helps. If there was a great demand, I’d spend the time combining (and updating) all of them into one plugin. But there isn’t – and other projects I am working on have higher priority. (Like my “CellarWeb Privacy and Security” plugin that makes a site more secure.)