My main motivation behind the switch was that I had too many daily reviews of very old cards that I knew well in Anki, after using the software very close to daily for several years. I read that SuperMemo handled older reviews better, and I was also optimistic at the time that the learning schedule really was better than Anki's (as SuperMemo uses a significantly later version of the algorithm that Anki is based on for scheduling reviews).

The software switch had its ups and downs. First, the downsides: a significant one-time cost included the time spent learning all the items from scratch, as the import of cards from Anki to SuperMemo didn't preserve the repetition history. Another one-time cost, though minor, was some friction setting up the software (it took an abnormal number of days to receive the activation code, which I eventually received after a follow-up; maybe the company had a problem with their system at the time).

Long-term downsides include the lack of easy image occlusion (aka, covering up parts of a labelled image and revealing just one label in separate flashcards). If I studied maps/diagrams with spaced repetition or anatomy like in my high school biology class, this would be a dealbreaker (though I suppose you could use keep using Anki along SuperMemo). In my experience, it's far easier to occlude images in Anki than in SuperMemo. Also, the Windows desktop version I use doesn't have a mobile version, which is a very significant downside. I'm now used to reviewing SuperMemo in the evening or when I think it's a good time, via software called Parallels to run a Windows virtual machine on a MacBook, but there's a lot more friction to starting a review session. To add to the friction, backups are a bit harder (though I've made it easier by setting up a custom keyboard shortcut to press the sequence of keys create a backup in a folder in cloud storage).

The main upside is that I do think (noting that I may have confirmation bias) that the flashcard scheduling really is effective and also more efficient. I no longer face significant numbers of very old reviews, and I do subjectively feel that I retain my cards better.

To add objectivity on effectiveness for accuracy, according to SuperMemo's data, I have a 97% retention rate on my French cards which contain a lot of very old cards, though I aggressively remake cards that become "leeches"; an 89% retention rate on my Spanish cards, which have much more newer cards; and a 93% retention rate on my mathematics/sciences/miscellaneous readings cards. Unfortunately, I didn't keep a records for Anki cards in comparison, and there may be other factors behind increased retention (if any) such as following better practices when making new cards [1]. I wish I had numbers for time efficiency, but I can confidently say that I don't dread spending time reviewing old cards (though once again, there may be some other factor).

On SuperMemo's other features: I also did try the "incremental reading" feature of SuperMemo, but ultimately, I borrowed some of the principles and stuck to a personal method of taking notes from different books, while switching between books (instead of only focusing on one subject a day) to help stay alert while studying the materials. There are also other features of SuperMemo for sleep tracking and task scheduling, but I didn't personally enjoy using them (I personally found that sleep tracking didn't account well for daylight savings, and I prefer other simple apps accessible by mobile devices for scheduling and task tracking).

To make a very long story short: I switched to try and reduce time spent during reviews, but ended up spending a lot more time setting up and getting used to the software. I didn't really mind the fiddling that much, as spaced repetition software was a sort-of hobby for me in the past, but for other people who'd just like to learn, Anki provides a far more direct way to try spaced repetition.

SuperMemo is effective for me now, as I don't spend much time at all fiddling with the software. But I'm not sure if I would enthusiastically recommend the switch to other people unless they're interested in spaced repetition software (and thus don't mind fiddling with it), and they also have some dissatisfaction with Anki in some way. In any case, with either software, I've found my studies to be more effective by treating spaced repetition as just a supplement to other forms of study that require active problem solving.

[1] Better practices included more strictly following Wozniak's twenty rules here (also relevant for Anki users): https://www.supermemo.com/en/blog/twenty-rules-of-formulatin...