Which Cisco firewall model is the latest: ASA or NGFW?

Purely from datasheet numbers, the Fortinet 400E unit has much higher performance in most dimensions than the 5525-X appliance, but you'd need to have some specific use cases and metrics in mind to know if that applies to you. If the key metric is a bang for the buck, Fortinet usually wins until vendors start applying extra discounts to level the playing field. Also, the 400E has been superseded by the 400F, using newer ASIC to effectively double most performance metrics, I suggest you have a look at the data sheets for that versus the current Cisco unit. As an engineer, I find the Fortinet units much more interoperable, whereas Cisco tends to encourage the adoption of their Cisco-proprietary solutions, as part of a single-vendor fabric. Also, for more junior admins, Cisco is a CLI-first solution and always has been, with ASDM feeling bolted on afterward, whereas Fortinet has a pretty good GUI in recent years, and only requires CLI for more esoteric features. The Cisco solution is always going to be a better fit if you want to know which solution your Cisco-trained engineers and admins need to best complement your Cisco routers, Cisco switches, Cisco WLC, and Cisco ISE. If you want throughput or port count for segregation, or a security-focused vendor with a more open feature set, Fortinet might be a better choice in my opinion.

I prefer Sophos. I find it easy to use and it has better features on malware and threat management.

I recommend Sophos XGS firewall. It will offer the best solution for malware protection.  Also, I recomend Sophos CIXA with XDR (Sophos Endpoint), so you can use Syncronized Security.