Join Date: May 2004
Location: formerly Gold now Diamond, formerly MSY, now LAX, formerly NW, now DL
Programs: Hyatt Plat, Hilton Gold, SPG Gold, Delta Diamond/1MM
Posts: 4,725
So I'm a lifetime SC member from the NW Worldclub days.
In general, the clubs are best of most Western airlines. UA hasn't changed since the CO days. Delta's lounges now have real food at all times, soups, salads, pastas, which is great. Plus, the well drinks and one craft beer on tap is free. Hubs and LAX do get crowded but still decently maintained in general. The agents are great when it comes to irropts too.
Lots of ways to access as mentioned above aside from getting a membership. Gold and above is ST Elite+ which gets you into lounges when you have a same day international flight. Also the AMEX charge card Plat or higher also has access.
Before Jan 1 2016, SC members got into AS Boardrooms but that's no longer a benefit given that DL has moved into direct competition with AS.
It depends on your $$ and alternative activities (airport offerings), but seems you travel enough that it's likely helpful.