Hi Sue and Marta,
Beyond v.13 - Can not recommend enough!
I was also a bit concerned about the upgrade but the functionality in Perform and Engage were far too enticing for our business. Even if you just use Learn, you and your users will have a much better experience that in v12 or before.
For example, the report builder is far superior to previous versions and the fact that they are dynamic when you open them make the system look much more modern than previously. There are also more graph options which can really set your site off.
I also personally love the seminar improvements and like the fact I can add my MS Teams account as a link in each of the seminar sessions which cuts down on admin in course arrangements amongst other great new functionality.
I would also mention the new multi-tenancy function which I don't use, but it is a real plus for companies who have different business units and want to keep the learning experience separate. With everything on Totara, you could use this for different contexts and really it is only your imagination that is limited.
I've managed our LMS (and previously Moodle site) for about 7 years now and I definitely think the biggest leap of functionality progress has been on V13. I will not lie, we went from V9 to V13 then to V14 6 months later and it was an enormous learning curve but the feedback I get from users about the enhanced experience was worth it.
I hope that helps!
Jill