Here's what I KNOW from owning several different diffusers.
1. The top one is a cold-air, ultra-sonic, almost silent diffuser. It is a good diffuser, but the one I had did not stand the test of time. It did not operate long and was not problem free.
2. I do not have personal experience with the second one you list, but it states that it is NOT quiet/silent and you are looking for one that is not too noisy.
3. This supplier of diffusers offers several different models. They do have ultrasonic diffusers. I have no further information on these, except for what is listed on their site.
4. The last diffuser you list is a good diffuser, but is noisy. I have owned this diffuser and it does a great job of diffusing essential oils, but the noise is an issue for me. This is not ultrasonic and diffuses essential oil from a well using a pump (NOISY).
The diffuser I am currently using is almost completely silent and easily diffuses even the heaviest of essential oils. It diffuses for 6 - 8 hours on one tank/8 ounces of water, while using only 15-20 drops of essential oil. It will diffuse a 700 square foot area/room.
I hesitate to include this link/information as my diffuser is sold through Young Living and YL is a MLM company. While it is alright for me to answer your questions about diffusers on CureZone, I can not link you to a MLM company to purchase products.
I have been diffusing essential oils for over 10 years and feel the information provided should help you make a more informed/educated decision when purchasing a diffuser, so I include this link.
Here is th link where you will find a PDF product information page. http://www.youngliving.us/pdfs/PIP_HomeDiffuser.pdf
A few things I consider when purchasing a home diffuser:
1. How much noise/sound does the diffuser make.
2. NO heating of the essential oils should ever be done.
3. Cold-air or Ultrasonic diffusing are my favorites.
4. How long will it diffuse before needing to refill.
One more thing. In MY OPINION ONLY... you should NEVER use an aroma/perfume grade essential oil in a diffuser. You do not want to diffuse adultrated oils/toxic chemicals into the air you are breathing. This is no better than using commercial air-fresheners! Diffuse pure, organic/therapeutic-grade essential oils.