Out of the two in T5A, last time, you were in the smaller one.

So, if you found that to be loud, noisy and very busy, the South club lounge is even bigger, so I don't like your chances of finding any more suited to your taste. The south lounge does, however, have some more "nooks and crannies" that you can go and sit in which take you away from the main throng of people.
However, the food will be the same and I imagine the noise level will be similar.

Why not take the chance to try both and see which one you prefer?

With your time scale, I think it might be a bit ambitious to go and try the B lounge too..