When you declare your ganancias annually, your accountant should calculate whether your expenditures are reasonable and advise you how much "white money" you have accumulated for future large purchases. If s/he doesn't do this automatically, request it. Be aware that AFIP is empowered by law to re-calculate your income based on your spending habits and then bill you for unpaid taxes plus steep penalties and interest. All accountants know the general formula, so they can protect you from under-reporting.
I've used Citi for several years. Routine discounts include 15% on everything in Carrefour on Tuesdays if you pay with a debit card (10% with credit card); same at Walmart on Wednesdays. Also 15% at Rodo and Ribeiro with interest-fee payments if you buy by telephone, and 10% on anything at Falabela. As mentioned above, they always have a big list of theater and cine discounts as well. The full current list of discounts is at
https://www.argentina.citibank.com/cmpgns/institucional/main.htm.
There are also occasional promotions. One day last week 80% of the stores at Paseo Alcorta were offering 35-40% off with up to 6 payments interest-free. Two weeks ago it was the same at Unicenter. I stocked up at Winery a couple weeks ago during a 40%+cuotas promotion.
Even bigger discounts are available with the private-bank Citigold service, which solves the typical problems with bank customer service and long-lines in exchange for steep monthly charges or high balance requirements. The 40% at Paseo Alcorta, for example, was for purchases with a Citigold card. They currently offer 25-30% off in some of the best restos in the city. You can see the offer at
https://www.argentina.citigold.citibank.com/cmpgns/programadining/main.htm?lf=cg.
Citi also offers the American Airlines credit card, so you earn miles at the official exchange rate (1 dollar-equivalent in purchases = 1 airline mile).
At the end of April, I received an advice from Citi that I had saved $13.269 in discounts during the prior 12 months. That seemed high until I did a couple calculations and found it's probably correct. (My purchases included some large items for friends without national credit cards.)
Comparing notes with friends using other banks, it seems to me that the competition, in terms of discounts, is Galicia, Santander Rio, and Banco Frances. You can find their current offers on their web sites. Compare them to your shopping habits to see which would give you the biggest benefit.