Honestly you can't go wrong in many neighborhoods. The only ones I don't like are in the downtown area. It's active during the day but at night it can get desolate and also when they have strikes or protesters it's almost always downtown. I just don't like that area at all. I also don't like San Telmo for living. San Telmo is also turning into "Disneyland" too. I feel sorry for the residents there as it used to only be on Sundays but it's extending to other times of the week too.
Much like I don't really like the heart of Soho to live in now. I spent 2 months there this summer and while it was convenient with many restaurants, I found myself more times than not, going to other areas. It's also filled with graffiti. My favorite neighborhood for everyday living is definitely Recoleta. When I permanently move back, I will ONLY consider Recoleta to live for everyday living. Everything you need is a few blocks away. It's a real neighborhood. I have my bakeries there, my coffee shops, florists, grocery stores, laundrymats. You name it and it's there.
I own an apartment in Palermo Hollywood and I also enjoy staying there when I go for work. It's in a great area and the building has 24/7 security. It stays completely booked solid so I rent it out when I'm not using it and then when I know I will go,, I block it out and stay in it.
If I lived there and retired, I don't think you will necessarily want to be where ALL the tourists live. Many expats are mostly poor and many are living in San Telmo and more affordable areas. I lived in Buenos Aires for 9 years and I never ever hung out with Expats. I had 100% foreigner clients and besides the occasional lunch or dinner with them, I only hung out with my local friends.
Much like now, I get invited to go to lunch or dinner or coffee about 5-7 times a DAY. I just don't have time to do that so I mostly don't. I typically will with clients of mine but I work a ton as I own many properties and I own companies in the USA, Mexico, Argentina. I'm also writing my autobiography so I don't have a lot of free time.
Here you can see all the neighborhoods of Buenos Aires -
https://buysellba.com/buenos-aires-neighborhood. You can click on the Learn More and see more detail about the boundaries of the area. The key thing is to just ask yourself what YOU like about the area and what is important to you as it will differ. I recommend renting some Airbnb in different areas before deciding where you want to settle down.
The #1 most important question to ask yourself if you're buying is "what is my main motivation for buying"?