Should I switch from Firestick?

I would say there is no need to switch – at least not right away.  TVs have multiple inputs and streaming devices are inexpensive and not mutually exclusive, so you can easily get one (or several), try them out, and see which you prefer.  I have a Roku, and an Onn Android box, and my satellite receiver and Blue Ray player can stream as well.  Of course, the services available on the last two are far fewer than the dedicated streaming boxes, but I mentioned them to point out that you can connect pretty much as many streaming things as you wish.

I prefer the Roku, but someone on an Android TV forum is likely to tell you he prefers the Android device.

As noted, you can easily use multiple devices. I have had Roku for awhile, but after cutting the cord, added a FireTV and Walmart Onn Google TV 4K Pro. Each has plusses and minuses, and there can be minor or even major differences in how an app looks and works between them.

For a Roku, do NOT get the basic Express. I consider the Express 4K+ as the minimum usable model.

First, the Fire TV user interface is heavily tilted towards Amazon content. If it don't bother you, then the only strong argument for moving to a Roku would be the availability of a specific app/service. There are some that are only found on Roku, but that's not an issue with the vast majority of popular providers. 

There are some differences between the Fire OS and the Roku OS. Probably the biggest one is the Roku will not permit installing any app that isn't available in their channel store, while the Fire OS allows installing Android based apps regardless of their source. Of course, you should be cautious installing any APK file that comes from an unknown source, as it could contain spyware and other not so nice things. 

Depending on the Fire TV device, it supports a wider variety of video and audio codecs, in case you have a home media server and play content from it. Roku devices only support a limited number of codecs and containers, and the rest require the server to transcode the files. 

The Onn is another Android based player, similar to your Fire TV, and will likely be able to play anything you currently have on your Fire. I have an older Onn 4K player, and it's a bit slow and buggy. They have now released their 3rd generation player, and have upped the price significantly. But I don't believe they have a Stick version of that player. 

The current Roku Stick 4K is a very strong performer, has good WiFi, supports Dolby Vision, and is currently on sale for $34.99, which makes it an outstanding value.