Cloudy weather would defeat the purpose so I am guessing that the western states would be more ideal due to greater chance of clear sky. Isolation would also be nice. At a camp site on or near a mountain top. Also, are there efforts to set up mobile solar observatories in the totality path?
I assume that when considering where to view the Solar Eclipse from, you're looking for the place with the best observance of totality. This elicits two factors, the degree of totality and the time elapsed during totality. The best observed eclipse will be a total eclipse, i.e., 100% totality, and for the longest time possible.
A map of the path of 100% totality is shown below. In it, you can see that grey band that passes across the US. Anywhere within that band, you'll be able to see a 100% total solar eclipse.
If you view this interactive map from NASA, you can see two specific points along the totality band that are called out, one labeled GE and one labeled GD.
The GE marker signifies the point of greatest eclipse which is defined as:
The instant when the axis of the Moon's shadow cone passes closest to Earth's center.
The GD marker signifies the point of greatest duration, quite sensibly defined as:
The instant when the length of the total (or annular) phase reaches a maximum along the central path of a solar eclipse.
So, if you're looking for the point of 100% totality that lasts for the longest amount of time, you'll want to be at the point of the greatest duration. Geographically, this is pretty close to Carbondale, IL.
You are correct that the western states have a higher probability of clear skies. NOAA analyzed historical data for August 21 and has a web page where they show a map indicating the chances of cloudiness in various parts of the country:
On that map, a white dot indicates a low probability of cloudiness, and the darker a dot is, then the higher the probability of cloudiness in that area.
On the same web page, they have an interactive map that shows the path of totality, and it lets you click on each dot to see the actual percentage chance that the eclipse will be visible, along with a breakdown of probabilities of clear skies, a few clouds, scattered clouds, broken clouds, and an overcast sky.
Based on that interactive map, it seems that Ontario, Oregon has the highest probability that the eclipse will be viewable at 93.3%: