How does it compares to Akamai Bot Manager to Defend Against Credential Stuffing ?

The best way to make a decision is to run a Proof-of-Concept exercise with both Akamai and F5 ASM.

If you are asking the community's opinion then my vote is certainly for F5, especially if you already have F5s in your infrastructure.

If you want a short non-technical answer then Akamai is more of a "one size fits all" approach while F5 ASM can be customized for your applications and your challenges and technically speaking there is no limit to this customization due to iRules (F5 scripts which can be programmed to do anything with the traffic and can be written and maintained by YOUR developers and network ops guys).

Another problem with Akamai is that when it starts blocking traffic it tends to block both bots and legitimate users trying to log in which of course will affect your image/reputation and availability. F5 ASM is far more granular (and can be as granular as YOU want it to be as YOU control the "bad traffic"/"good traffic" selection and blocking process).

Another issue with Akamai is the time it take to implement changes. I had bad experience with them taking over an hour to implement a change to roll out traffic rules to protect my client from a massive cyber attack. That was an hour of downtime of a busy site used by millions of paying customers. Caused lots of lost transactions/financial loss. How much does an hour of downtime cost your business? When my client switched to F5 a similar manual rules roll-out took less than 10 minutes.