I'll chime in on this one...
First of all. To the statement of Crystal Focus being "the best". While it's true a large portion of the community may agree with this statement, there are plenty who wouldn't. There are many options out there that all do great things in there own ways. The only way to find the best is to find what YOU like the best.
Now.. on to what's better about a CF4 VS CF8-9. This is something some simple forum searching will show you. long story short, as the board has iterated over the years it has added many features. The one that's coming out in a few weeks is the CF V10 (or CFX). It will have a feature on it called Smooth Swing. This feature is new to Crystal Focus ( and currently exclusive to CFX ) BUT Smooth Swing is not new in the community. I would suggest also doing a history research on that as it goes way back.
Besides crystal focus soundboards... Other great options are the Spark Soundboards from Naigon's Electronic Creations AND the Proffie Open Source soundboard.
Each soundboard has its own way of configuring and setting up. The Proffie board is Open Source so it does come with a higher learning curve BUT the trade off is that you can virtually do anything with it. You could literally code in your own features if you know what you're doing. :)
Also in the way of the (smooth swing feature), The Spark soundboard from Naigon now supports Real Swing which is their version of Smooth Swing. It's not Smooth Swing because it works entirely differently.. BUT the end result is very similar. *Also should do homework on this as how they are developed and the algorithms they use are different too
In closing - The soundbaords mentioned above are regarded as the top 3 for the most part. There are lots of others to consider as well and more coming out in the future. This hobby, as you will learn, is quite packed with info. If I had one piece of advice it would be to get comfortable reading! lol. A lot of us are happy to answer questions, but there really is too much info out there and most always you're better off reading and looking up on the forums. I only say this from experience, because usually with a simple search you'll find the anser.
Lastly, I also cannot emphasize enough that the words "better and best" are subjective. Until you try out each soundboard for yourself, its impossible to know what you will like or not. And your favorite isn't everyone's favorite. It's kinda like Apple VS Android in most cases... MOST that is, not all haha. but the point is, Lots of great boards with lots of great features! Check em out and see for yourself :)
And welcome to the hobby!!!
-LINK