I have both United Club and Priority Pass Select memberships.
Within the US, PP Select has a fairly small number of lounges available, and if you're flying United then there's a good chance that when lounges are available they will be in another terminal and/or not accessible.
LAX is probably their best airport in the US (if not worldwide!) in terms of number of lounges, but as LAX only allows you to enter the terminal you're flying from the only option when flying United is the Alaksa Airlines Boardroom in Terminal 6 - which thankfully is a good option and is better than the UA option IMHO. (They also used to give access to reLAX which was land-side in TBIT, but that's gone from the list now).
Places like Chicago, JFK, and many of the others you've listed you're simply out of luck - there are no lounges in parts of the airport you can access when flying United. At IAD there is one (BA), but it's in the A/B concourse so a good distance from United, and it's only open very limited hours...
There are a few exceptions, such as San Jose (CA) where there is no United Club, but there is a conveniently located Priority Pass lounge.
Personally, given the choice of the two, I'd go with the United Club membership, or potentially look at a full Priority Pass which is cheaper than UA (plus they often do 10-15% off specials) and gives you access to most United Clubs as well - just without a (free) guest.
Originally Posted by
Deltahater
Priority pass lounges seem to be a step down from airline lounges. Plus they only allow guests for a $27 fee.
That depends on the specific membership you have. The full card charges for guests, but some of the Priority Pass Select cards include 1 free guest as well.