Oooh Lucky you!!!!
Ive spent a lot of time in Rio and BA but Punte del Este is definately on my hit list.
Rio for NYE is spectacular by all accounts but gets ridiculously busy - though that does have its own appeal. Would chose that for NYE over BA by all accounts but not too knowledgable on how good Punte Del Este is for NYE specifically although it should be heaving in general around that time.
In addition to the places you've listed I would make a trip down to Warung Beach Club near Florianopolis in Brazil - is the most spectacular club in the world IMO and gets good line ups. Saw Sven Vath there last year although this was around carnival so you would need to check the line ups.
Rio - clubs tend to be either glam where the rich and beautiful of Ipanema hang out - but playing commercial house and brazilian music - Best clubs for this are Baronetti in Ipanema, Nuth in Barra Ta Tijuca or ZeroZero in Gavea
or the more bohemian parties with lots of Samba and Brazilian or Baille Funk (amazing beats) - Best for this is to head to the area called Lapa which is awesome on a weekend.
There some house clubs as well which are good though we went to special events that were thrown mainly during carnival. Electronic music is mainly gay/mixed scene in Rio - Had a lot fun but did get my ass pinched by a lot of ridiculously toned and scary guys
Try and catch an X-Demente party which happens once or twice a month at Fundicao Progresso - basically a massive rave, or go to Dama de Ferro or Fosfobox in Ipanema which are good dance clubs but to be honest would wait until Buenos Aires for dance music as the scene is much bigger there.
There is also a more traveller / Beach party scene away from the main cities if you want to go further north up the coast to places like Arial Adjuda or Morro De Sao Paulo or much closer to Rio, somewhere like Buzios which is very expensive but stunning. Although will be very similar to Punte Del Este I imagine.
BA- As I said much more Dance music focused and as close to the Ibiza/Spanish crowd you will find anywhere in the world
Club wise Pacha is a must. Prefer it to the Pacha Ibiza any day. Also worth checking out is Bahrain which plays really good filthy techno in the downstairs bit. Other less serious places are Crobar
Niceto is good as well (On a Thursday I beleive) - the night is called Club 69
Again the "glam" clubs worth checking out are Mint & Rumi and probably a whole lot more which should be easy to find out about (although Mint does good dance music nights too).
Pick up a copy of a free weekly listings paper like Wipe when you are out there for more up to date stuff.
Oh and Dont go to Opera Bay (its Rubbish and overrun with tourists!)
Well hope that helps, though feel free to ask as I could go on and on!
