Tried them all. A packed tool bag on the rear fender can also make it hard to swing your leg over the bike to get on. May not be a problem on level ground, but if you dump it on some nasty hilly single track, it can be annoying. Plus it can smack you in the butt on whoops.
If you like to carry a lot of tools, maps, extra oil, a sandwich, snacks, etc... the front fender bags are not big enough and more diffiuclt to access than a fanny pack or number plate bag. They are Perfect for a spare tube on a long multi-day ride, but not much else, IMO.
The front number plate bags I've used really bounce around if you have anything heavy in them. It's distracting and annoying on the trail. They are easy to get to, though.
All in all, a decent fanny pack is the most versatile and best option for me. I don't notice mine much when riding. Rather than getting hurt by the fanny pack in a fall, it's more like extra padding, IMO. Easy to pack and access, plenty of sizes available, etc...