SaneBox is great for anybody who a) gets a lot of emails, and b) needs to respond quickly to email. For example, as a consultant, it's important that I quickly read and respond to my clients' email messages. SaneBox would be less useful for people with low volumes of email, or where there is little or no email from external senders.
Thunderbird is a great solution if you primarily work on the desktop. I like knowing that Google isn't snooping around my emails to sell me things I don't want or need. It's relatively easy to use, but can be tricky to install and sync with other email services like Gmail. If I didn't have a technical wiz for a partner I'm not sure I would have started using it in the first place. You do need some kind of technical ability to install, troubleshoot, and backup.
I use the Snooze and Spam features in Office 365 for another mailbox. I feel SaneBox's system of folders is easier to manage, plus it is available from anywhere I check my email. Office 365 snooze is not available through my Android email program and in [my opinion] it's aggravating not being able to organize email from my phone.