Some add-ons are available no where else but on Firefox. You can customize it, add themes, personas, and tons of add-ons to do just about anything.
If your looking for the most user friendly/choice browser that won't spy on you, then Firefox is certainly the best. They give away free stuff to use it to data mine it's users. I would say their software is safe, just not your privacy with using anything they have. They do install a root level updater that updates all their software which many people later have problems with and is certainly questionable as being unnecessary intrusive. Google isn't know for respecting a users privacy, and have been fined and busted by many governments over their tactics. It's safe to download, however it all depends upon what you consider 'safe'
