Comment by zahllos

> I didn't see actual benchmarks, but Serpent sounds at least three times slower than Rijndael

You can read the original report on the candidates: https://nvlpubs.nist.gov/nistpubs/jres/106/3/j63nec.pdf

To save you some time, one software evaluation is on page 531. Serpent performs worse in software than Rijndael (AES) just about everywhere (note they use categories rather than precise metrics, but you can dig into that if you want). By contrast, one hardware evaluation is on page 539. Serpent has the highest throughput for the lowest "area" i.e. required. These results repeat on p541.

So it depends on whether you are comparing a software or hardware implementation.