
This is rather a subjective issue. The answers slightly depend on what sort of site you have, and how much data needs to be backed up. One thing I will say though - please ensure that you back your site up somewhere (and not in a sub-directory of the same server). Most of the plugins below have scheduling available, so there is no reason to not keep regular backups. Some of these can also come in handy if trying to migrate to another server location.
Updraft Plus has been around for quite a while - they call it 'the world’s most trusted WordPress backup, restore and clone plugin', and they're probably justified in feeling that way about it. Having used it on a large number of sites, I can confirm that it is extremely reliable, and even works well on low performance servers. The free version includes sheduling, and you can upload backups to Dropbox, Google Drive, OneDrive, Amazon and generic S3, Microsoft Azure, Google Cloud, BackBlaze - they also offer their own UpdraftVault storage. The only thing to bear in mind, is that the free version sends backup files all into the same directory, so if you're backup up multiple files it can get tricky to find the ones you wnat. Updraft Plus have addons that allow you to create sub-directories for each site, but this comes at a cost. If you're managing lots of sites this canget quite costly. A sneaky tip here - if you backup to an S3 service (I would recommend Wasabi), then you can generate separate folders without an addon.

I've only recently become aware of WP Vivid, but their plugin gets 5 star reviews pretty much across the board. The free version doesn't have scheduling included, but the pro versions are very good value - they even have a lifetime licence that works out cheaper than the Updraft Premium annual subscription that offers almost the same functionality. I have tested WPVivid fairly rigorously across several sites of differentsizes, and it's been very good. It's a tad more tricky to setup than UpdraftPlus, and has a lot of features that some might find confusing. However if you persevere with it, it seems to be very reliable. I have noticed on large sites with low resources, it sometimes times out, which I havent noticed so much with Updraft Plus. However if you have a large site on a low performance server, then it may well be time to look at changing your hosting!

Vaultpress is now part of JetPack, but can also be purchased separately. It is developed and managed by Automattic - the same people who own WordPress itself - so they should know what they're doing. Vaultpress works slightly differently from a lot of other backup plugins, in that it backs files up incrementally. The first backup can take a long time, but then subsequant backups only include changes to content or uploads or plugins etc. This makes backups much quicker and less resource intensive. If you have a very large website, this sort of backup solution may well be a good option. Vaultpress also comes with an added benefit of File Scanning, Automated File Repair, Scam Defence, and site migration. It can be a little tricky to get it setup, but it's very much a set-and-forget plugin. My only criticism, would be that restoring a site from Vaultpress can take hours, and it's not possibly to easily download the backups from their storage (as far as I'm aware anyway).

WP Time Capsule works in a similar way to Vaultpress, and backs up files incrementally. It is also quite to slow when making the initial backup, but speeds up a little when making subsequent backups. My feeling is that the subsequent backups are not really as fast as they could be though - especially as it's only backing up changes. However, it does seem to work quite well. Like Vaultpress, restoring is painfully slow.

Backup Buddy is from the same developers as iThemes Security. This is a very polished backup plugin, and the settings are all very clearly laid out. I really want to like this one, but I have to confess that every time I've tried it, it's failed to be be reliable. This is a shame, as I think it could easily be a valid competitor to the other leaders of this pack, but it's not for me. I suspect that it may well have something to do with my hosting company's server settings, so your experience may vary. iThemes offer their own cloud storage called 'BackupBuddy Stash' - 1GB is included with the Blogger version, but you can buy extra space. The plugin will also upload to Amazon S3, Google Drive, Dropbox (but not Wasabi as far as I can tell). They don't offer a free version, so there's no way to try it out before you buy.

Duplicator is, as the name suggests, designed for cloning a WordPress site. That being said, it does also have the option for scheduled backups. The plugin is hugely popular, and has over a million active installations. It's extremely good at migrating WordPress sites from one server to another. However, I've tried using the scheduled backup functionality, and not had much success - again, others may find it works fine for them. I have also found that I often get timeouts when trying to package up very large sites.

BackWPup has over 600,000 active installations, so is evidently quite popular. I have to confess I've not tried it, and I doubt I ever will. Their pricing model is designed more at the single site user rather than someone who manages multiple sites. The free version of the plugin probably works well, but it doesn't include the ability to restore the backups, (you have to go pro for that), and the annual costs are quite high by comparison to the other backup plugins.

This plugin is hugely popular, but is more geared towards migration than scheduled backups. The community edition will only backup a site of up to 512mb, and doesn't have the functionality to restore the site. As soon as you want to go higher than this, you need to go for a subscription, and unless you're purchasing the plugin for personal use only, this get's very expensive.
Akeeba started life as a backup plugin for Joomla. However, they've now developed a version for WordPress. 10 years ago, when I was responsible for managing a few Joomla sites, I found that the Akeeba backup solution was the best one available. I haven't had a chance to try the WordPress version so far, but if they've built it with the same care and attention, then I imagine it will be pretty good. It's also competitively priced (much cheaper than some), and I'll be interested to see how this one fairs in the long run.
For me the choice usually comes down to Updraft Plus or WP Vivid. Updraft Plus is extremely reliable, especially for larger websites, but it get's expensive when you pay for the pro version. WP Vivid is excellent value for money, and has a lot of features. I've found a few niggles with it, but once you get the settings right, it seems to also be very reliable - you do have to pay for the scheduled backups though. If you don't need any of Updraft Plus's pro addons, then you may well find it's the best choice out there. If you need a few more options, then WPVivid may be slightly more economical.
For extremely large sites (i.e. over 1GB), then it might be worth thinking about using Vaultpress of WP Time Capsule. The incremental backups may be sluggish, but they don't use as much resources and will be less prone to timeouts.
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