A very important one I can see is that Blade targets back to Java 6, whereas Spark only targets Java 8. This makes it available on slow moving platforms like Google App Engine.

It would be the forever (especially in Javascript frameworks); why don't more people combine forces instead of doing their own thing? But then coders have opinions which do not fit the other frameworks (like they don't like the deps or coding style or usage patterns) and then they roll their own while the alternatives are perfectly fine for most.

I have been using spark since 2013. One thing that I see that this framework provides in DSL for DB like operations. In spark you have to configure out of the box