Disclaimer: Never used Ibis before but I daily use polars and DuckDB.
It seems like Ibis uses DuckDB on its backend (by default) and has Polars support as well. Given this, maybe see if Ibis works better for you than polars. If you very specifically need polars, using that will for sure be better. DuckDB is faster than polars and it has great polars support, so depending on how Ibis is implemented it might be "better" than polars as data frame lib.
Whether or not DuckDB is faster than Polars depends on the query and data size. I've spent a large portion of the last 2 years building a new execution engine for and optimizing Polars, and it shows: https://pola.rs/posts/benchmarks/.
