I have stayed at the Club level on all 4, and my personal ranking is:
1. ITC Maurya - in the ITC One Wing (not the "Towers" or the "Executive Club")
1. Taj Mahal - small lounge, but very good service. Especially nice are the freshly squeezed fruit juices available all day, in a variety of seasonal choices.
3. Taj Palace - newly renovated, but somehow seems a little cold compared to the Taj Mahal.
4. Le Meridien - an average business hotel lounge.
(Note that the first two are a tie at 1, and not a typo!)