Unpredictable performance – you never know if your user will open and ‘compile’ your website on a mobile device with a very slow internet connection or not updated browser
Client-side routing solutions can delay web crawling
SEO – if you didn't implement correctly
Some or all content is not included during the first loading
SSR
Pros
SEO friendly – SSR guarantees your pages are easily indexable by search engines
Better performance for the user – User will see the content faster
Social Media Optimization: When people try to post your link on Facebook, Twitter, etc. then a nice preview will show up with the page title, description, and image.
Shared code with backend node
User-machine is less busy
Cons
TTFB (Time to first byte) is slower; your server has to spend some time preparing HTML for your page instead of sending an almost empty HTML doc with a link to javascript
The server will be busier, can execute fewer requests per second
HTML doc will be bigger
The page is viewable sooner, but it’s not interactive and in the beginning, a user has to wait until react will be done executing