It usually not a good idea to change brands "just for a change". Juniper is a good device, even the smallest model (SSG5) allows for 8000 sessions - so what they need licenses for?
But if they want to do a change, the famous ones come into mind: WatchGuard (easy to manage, reliable), SonicWall, CheckPoint (which has been a bit - proprietary, but are much better lately).
There is no "Best solution", it depends what they want to do with it, who manages it, how much the budget is, what the demands in future are, and lastly on personal preference. Some folks like to use the GUI, others CLI, and I do both - Juniper SSG allows for that.