Concur, TK > LH > UA. But with four hours, you might as well see them all. The TK lounge's advantage is greater early in the day; until early- to mid-afternoon, the food at LH isn't that special. Bar service is better there, though.

If you have a Priority Pass card, the AF lounge by the A-concourse train stop is also worth a visit before it closes to PP guests at... what, 4 p.m.?