The main difference is the PTFE is no where near the hot zone which overtime can wear the PTFE and caused leaks. This is more important when printing higher temperature materials due to limited temperature resistance of PTFE.
As a note, for all Metal Hotend, you need to ensure the nozzle and heat break is hot tightened to prevent leak due to thermal expansion.
Image Source: https://recreus.com/gb/noticias/learn-with-recreus/filaflex-vs-all-metal-hotends