We've just given my 5yo DS a Yoto mini, I don't know much about Tonies. So I can only really give an opinion on Yoto.
It's amazing, he's completely obsessed with it. I like the podcasts- there are loads available via the app, you can link the podcast to a blank card and then it updates automatically with new episodes. My son has a card for CBeebies radio, one for the Sea Life podcast, one for a children's football podcast.
And the podcasts are free from the app, so we haven't actually had to buy any content yet as he's still enjoying trying new podcasts from the app. There are baby/toddler options on there too, and plenty of options that would suit much older kids, so I feel like it has longevity. The design isn't too babyish, and I think it's quite clever that they've designed a product that is usable and enjoyable for babies through to upper primary.
I wouldn't worry about the cards too much. They're sturdy and extremely easy to put in the slot.
It also has some quite useful control features- I can use the app to preset the brightness/volume. So, for example, if 7:30 is the time I want him to wind down to sleep, I can set the Yoto so that it won't go above x volume after 7:30 at night. Or I can set it so that it won't go above a certain volume on earphones.
Highly recommend!