What are the advantages and disadvantages of an all-metal hot end compared to one with a PTFE heat break?
This is a good question to make a comparison table. All-metal hotends Vs. PTFE liner hotends.

All metal:


Works well for high (+250ºC) temperatures filaments like nylon or PC.
No need to replace the PTFE liner (pretty obvious).
Retraction performs worse.
Plastic can get stuck to the inner walls. This can lead to clogging, more likely when changing from ABS to PLA (higher temp plastic to lower temp plastic).


PTFE liner hotend:


Limited working temperature. Above 250 PTFE will start to degrade.
PTFE tube needs to be replaced more or less often, depending on the use of your printer.
Retraction performs better.
Plastic is less likely to get stuck in inner wall (PTFE is very nonstick).
When using PTFE liner, the plastic is melted very close to the nozzle. Unlike other techniques, in FFF/FDM 3D printing this is more desirable. E.g. to avoid 'heat creep', for a better flow control and more accurate output dimension.


Of course there are more points to compare. Please comment to add any other useful point.