What's wrong with Pandas?
Since Pandas lacks Polars' concept of an Expression, it's actually quite challenging to programmatically interact with non-trivial Pandas queries. In Polars the query logic can be entirely independent of the data frame while still referencing specific columns of the data frame. This makes Polars data frames work much more naturally with typical programming abstractions.
Pandas multi-index is a bad idea in nearly all contexts other than it's original use case: financial time series (and I'll admit, if you're working with purely financial time series, then Pandas feels much better). Sufficiently large Pandas code bases are littered with seemingly arbitrary uses of 'reset_index', there are many times where multi-index will create bugs, and, most important, I've never seen any non-financial scenario where anyone has ever used Multi-index to their advantage.
Finally Pandas is slow, which is honestly the least priority for me personally, but using Polars is so refreshing.
What other data frames have you used? Having used R's native dataframes extensively (the way they make use of indexing is so much nicer) in addition to Polars both are drastically preferable to Pandas. My experience is that most people use Pandas because it has been the only data frame implementation in Python. But personally I'd rather just not use data frames if I'm forced to used Pandas. Could you expand on what you like about Pandas over other data frames models you've worked with?
I like how in Pandas (and in R), I can quickly load data sets up in a manner that lets me do relational queries using familiar syntax. For my Elite: Dangerous project, because I couldn't get Pandas to work for me (which the reader should chalk up to my ignorance and not any deficiency of Pandas itself), I ended up using the SQLAlchemy ORM with Marshmallow to load the data into SQLite or PostgreSQL. Looking back at the work, I probably ought to have thrown it into a JSON-aware data warehouse somehow, which I think is how the guy behind Spansh does it, but I'm not a big data guy (yet) and have a lot to learn about what's possible.
I’m actually quite partial to R myself, and I used to use it extensively back when quick analysis was more valuable to my career. Things have probably progressed, but I dropped it in favor of python because python can integrate into production systems whereas R was (and maybe still is) geared towards writing reports. One of the best things to happen recently in data science is the plotnine library, bringing the grammar of graphics to python imho.
The fact is that today, if you want career opportunities as a data scientist, you need to be fluent in python.
Yes, there is Octave but often the toolboxes aren't available or compatible so you're rewriting everything anyway. And when you start rewriting things for Octave you learn/remember what trash Matlab actually is as a language or how big a pain doing anything that isn't what Mathworks expects actually is.
To be fair: Octave has extended Matlab's syntax with amazing improvements (many inspired by numpy and R). It really makes me angry that Mathworks hasn't stolen Octave's innovations and I hate every minute of not being able to broadcast and having to manually create temp variables because you can't chain indexing whenever I have to touch actual Matlab. So to be clear Octave is somewhat pleasant and for pure numerical syntax superior to numpy.
But the siren call of Python is significant. Python is not the perfect language (for anything really) but it is a better-than-good language for almost everything and it's old enough and used by so many people that someone has usually scratched what's itching already. Matlab's toolboxes can't compete with that.
Finally, as someone who wrote a lot of R pre-tidyverse, I've seen the entire ecosystem radically change over my career.