I am of the opinion that if you are going to go for a redemption in UC you should go for the longest flight, to get the most out of it. LAS redemptions are hard to get, but LAX and SFO are easier, and SFO has a clubhouse of the two.

That said, having spent nearly four hours in the BOS clubhouse on Friday it gets my vote for the currently best of all the US clubhouses (BOS, JFK, EWR, IAD, and SFO) - I've been in all of them in the last three months too. Here's a compare, a very subjective one:

BOS - small but lovely though can get busy, great staff (the best), love the deli options - not a lot of hot food but all else is really good, well equipped, close to the gate, the best interior design at the moment

JFK - large, open to the terminal (rumour is that a new one is coming in 2011 with private security channel!), showing its age, especially in the loos / showers, good bar, nice views, I always find the food a bit humdrum, magazines are great if you limit yourself to golf and property, a hike to the VS gates and security can be dire

EWR - in the terminal and large but no windows, always like the dining, among the best hot food anywhere in the network, staff always charming, no showers, not the best for working in, always well timed when they announce flight departures, I think it's better than most people do

IAD - very good but often find the staff a bit elsewhere, spacious with good views, right opposite the gate VS uses, food middling, good for working, shower, and at IAD there are still smoking rooms so no trips landside (which you wouldn't do) for a puff!

SFO - seating amongst the most trendy (ergo not comfy for me), great bar, concierge staff (Claire) among the best, food OK, views OK but no runways, gets busy with VXers (although isn't VX moving terminals at SFO soon?)

As for LAX - well VS uses the ANZ Koru lounge which clearly isn't a clubhouse but is a great lounge, I like the design, the simple food options are well done, NZ wines on offer (and frequent specials) are GGGreat, and it's very well equipped - but again can get busy especially when the NZ1 / 2 overlap with the VS7.

Avoid MIA - hideous Club America, ORD VS uses the JAL lounge which is very basic. Can't speak about MCO, would never go there, LAS I would connect through LAX or SFO.

Oh, and of course get to the LHR clubhouse really early, have a champagne mohito and a massage (even at the same time!).