A FlyerTalk Posting Legend
Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 100,409
I don't think DL yet has a lounge at DEN.
If OP will be traveling a lot on UA from DEN, by all means get something to have a UA lounge membership, which is likely to allow use when you're flying some other carrier too.
Start by reading your company's travel policy very carefully. Are UA and WN your preferred airlines or not?
If DEN has CLEAR, the fee might be worth it. I've seen long PreCheck lines at DEN.