Ask HN: ExtJS GPL 4.2.x or ExtJS GPL 5.1.x ?

Hello, at work I'm about to embark on a project to update the web services we have (for in-house purposes) as the back-end for a portal site for functional and technical queries. I'm going to use ExtJS, because it has the "best" data grid implementation available for free, with filtering, column rearrangement, and sorting galore. Given that ExtJS 4 has been around a lot longer and there are more examples and discussions about using it lying around on the web, is there sufficient reason to use ExtJS 5 yet, or am I better off (at this point) sticking with the version with the most "community" support? Advice please! (especially if you've found yourself in the same or a similar position...) gjvc