I'm a little bit confused about the terminology. Are we talking about the Kindle Fire HD range of tablets, or the low-end, $50 Amazon Fire? Our family actually owns both types. I have a Kindle Fire HD 7 and my daughter has an Amazon Fire tablet (which I purchased from Amazon on Black Friday last year for $25!).
Both have upsides and downsides, but my Fire HD is several years old now and I'm sure there are new features so I'm not going to comment about that tablet, since it's kind of obsolete. The battery life on the old tablets is amazing though, like I said, it's several years old and I use it daily and I've only just recently started to notice that the battery isn't lasting as long.
My daughter's Amazon Fire is an amazing value for the price. I did expand the memory on it, I had to because she filled up the memory within the first couple days of owning it, she loves making videos of herself playing with toys or doing things outside. I put a 32 gig card in it and she hasn't run out of space in the last year and a half. The screen is kind of small, but it's lighter than my Kindle so I prefer reading on her tablet. The experience of reading on a tablet isn't as good as an e-reader, the tablet is good for all-around versatility though. Amazon doesn't get all the same apps as Apple and Google Play, so there's no Pokemon Go for Amazon tablets and now my daughter is asking for an ipad so she can play that dumb Pokemon Game.