This was a difficult comparison to make. After spending a few years on this forum these are the main brand/model choices that most people go with. There are other brands and other models, but these are the most popular. There are so many exceptions to these basic attributes that I almost did not post this. This is an important point. For example with Acurite Atlas Access I list it as not offering a WiFi capability but if you wanted you could add a WiFi bridge from 3rd party router manufacturer. There are sometimes ways around some issues. Please feel free to point out any mistakes.
I initially did this for myself but I've decided to share it. This comparison has a focus on what you'll miss or what are some major differences.
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* UPDATE: Ecowitt will soon release an SHT35 chip sensor model WH32-EP (May 2020) for outdoor use, and WH31-EP for indoor use.
** ObserverIP no longer recommended. Just stick to the GW1000.
This comparison was done in an attempt to show that there is no best weather station that checks all the boxes for everyone at any price. They all fall short. Even Davis VP2 a major drawback is the price premium and dated black and white LCD display. Many will say that the price is worth the years of service. But Davis temperature and humidity sensors on average last 18 months (give or take with some exceptions) and then they need replaced at ~$50. For many people though the Davis humidity sensors have lasted 5 or 6 years. But the rest of the unit is a tank. Unfortunately the Davis Vue does not have a cost effective replacement temperature and humidity sensor as you are practically replacing the entire outdoor unit at a much more expensive price upwards of $160. The Vue is the only one of these I would not recommend, I'd say you are best in the Ambient (Ecowitt) and Acurite range or go full boat with a VP2. The Vue is sort of the middle range that eh, in the long term not worth it, for a bit more you can have a VP2 without UV and without solar (like the Vue since it doesn't have those features).
This thread is not intended to start any fanyboy wars. This sort of information should be easily available. It is not uncommon for technical publications to make product comparison Pros and Cons. Let's add to the conversation with meaningful analysis and solutions. Every manufacturer could learn a thing or two from the other companies and do things better. Acurite could learn that people shouldn't have to jump through hoops (intercepting network data and running Linux) to get at the data locally to publish the data to other online services, personal websites and 3rd party programs for analysis. Ambient could learn to put better sensors instead of lowly SHT30 that work well in most climates unless you are in a dry weather region. I already mentioned Davis with their dated display but something else they could do is change their sensors to be I2C compatible so that we could replace sensors for better models like SHT35 / SHT85. There are many more things they can all learn...these are just some examples to show that they all fall short. These are things that are not in this initial basic comparison.
It is important to also realize that there is personal choice. Nothing should be compared just at face value. Different things represent value to different people. For example for me an important feature may be ease of data acquisition for other 3rd party software, but for someone else having better wind sensors may be more important, or product durability, or maybe they just prefer to support an American company. My point is that there are many more things to keep in mind. For some they just may prefer myAcurite.com over Ambientweather.net or Weatherlink.com which are each perspective companies cloud service.
I thought of adding a long list of Pros and Cons to each. But maybe that can be done by all of use with follow up posts.
We all win if these companies continue to learn and put out new products when they see that all of these things matter to us.
If you are an undecided user to this forum and are buying your first or next weather station hopefully this thread will help and not turn into some crazy war.
UPDATE: This post is outdated information. Things change fast. For example there now is a lightning sensor option for Fine Offset clones. There are now ultrasonic anemometer options for both FO clones and Davis. Many more new sensors are now available like PM2.5 and more. This thread is not sticky because it would require maintenance and constant updating to keep information current. Besides this thread was started with the intention that users share their grips about the station that they owned and nobody wanted to share the cons of what they own. I wanted to hear about both pros and cons but people are too proud and blinded by their investment decision to not want to dis on what they own. I saw it as a way to make it known to the manufacture that there was something that should be improved. But I guess not everyone thinks like me.