Stronger than the corruption/crimson ones in damage and is available earlier
The Underground Jungle (the only source of vines and Jungle Spores needed to make the Amazon) is generally considered more dangerous than the Crimson/Corruption. Survival chances in such areas without post-EoW/BoC gear are fairly low unless you're really good. As such, items crafted from UJ materials are more powerful than those gained from other places.
it's range can also be patched with a string accessory
That's one of the principle downsides of YoYos, not an advantage. To make them really good, you have to burn at least one accessory slot on them.