Hardened Empty Bottle costs 0.1 additional Silver Shards over Transparent Empty Bottles to manufacture. This isn't a very a very high price if there are any real benefits to using them. What are the benefits? It saves time. I've timed myself bottling water and it resulted in approximately 22% reduced gathering time.

"But that's obvious because it says so right on the bottle description!" you cry. Well, the description for the Transparent is -7 seconds and the description for the Hardened is -10 seconds. If we take this literally, it will take negative amount of gathering time for each, since a normal bottle already takes less than 7 seconds to use. With the descriptions being less than clear, an experiment does make things more... transparent. And give us some... hard evidence. I'm sorry, I'm sorry! On with the setup.

It's simple really, I used 60 Transparents, clicked a stopwatch at the start of gathering and at the end. Then did the same for Hardeneds. I had +2 gathering speed from food effects during the time, and my Bottling mastery was 704 with Gathering mastery 390.

Gathering times for 60 bottles:

Transparent Empty Bottle: 199.29 seconds

Hardened Empty Bottle: 154.69 seconds

As you can see, the quantity was about the same. 121 vs 122 Bottled River Waters.

In conclusion, it's probably worth it if you often find yourself in a hurry to bottle some water, so that you don't have to wait around. Otherwise, if you like to AFK gather, then you'd save the effort of finding some silver shards by using transparent empty bottle. If you like to AFK gather for even longer, then you can save even more effort manufacturing and paying the black stone powder by using the basic bottle.