Honestly you will regret any of those.
I tried a similar dehumidifier to the photos you added and it definitely could not keep up with the moist air here. It was pretty much worthless.
I have a 3x3 and we often have high humidity where I live. I have found that I absolutely must have a way to keep that number down and at a steady RH. I took a chance with an Ivation 13 pint unit that has worked nearly flawlessly for my situation. I would like the luxury of controlling the entire room as Aqua Man suggests, it's just not practical in my situation and I needed something that I could fit in the tent. The Ivation 13 pint fits this requirement (just barely!). I also wanted something with a humidistat that would allow the unit to automatically come on and turn off to keep the RH more consistent and stable. Again, the Ivation delivered.
The only flaw that I have observed in this unit is that the lowest RH setting is 35% and it does not kick in until over that by 5%. I have found that during high humidity days, especially after I water, it has a hard time keeping up with the humidistat set to 35%. However, it also has a continuous on feature which basically has the unit on all the time, and on those days when I need a bit more from the unit, I switch it to continuous and it pulls the RH down to 30-40%, which is right where I want it now that I am in full on flower mode with my plants. The other drawback to having the unit in the tent is that it does put out some heat. I also have an 8" inline fan pulling air out of the tent as well as fans circulating air in the tent. Having A/C in our house is also helpful in keeping the temps down and during this HOT summer, absolutely essential.
You can see the Ivation unit in some of the photos of my grow. Like I said, it barely fits. If I were using the 3 gal pots, it would fit a lot easier, but I like the idea of giving the roots more space so I went with the 5's.
Here is a link to the unit I speak of. Hope this helps!
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