All-metal hotends are less forgiving / not as good for PLA -- but how bad? Currently, I'm using a Creality printer to print PLA (that's what I have on hand) but I'm definitely interested in working with other materials that require higher temperatures (both much higher, and just enough higher that the stock hotend is very marginal) in the future. 

I understand that all-metal hotends are less forgiving and that they particularly are not the best for printing PLA, and shouldn't be assumed to be an upgrade when only printing PLA. 

What I don't understand is, how bad are they? Are they so bad that I should plan on changing back to a PTFE hotend whenever I print PLA or ABS? Or are they suitable for use on a printer that is sometimes used for printing PLA and ABS and sometimes printing high-temp filaments?
All-metal hotends are less forgiving 


Yes 


  not as good for PLA


No


  but how bad?


That is very subjective and totally depending on the skill of the 3D printer operator! So, that part of the question cannot be answered.

Fact is that all-metal hotends are sold as being upgrades to lined versions, this is simply not true. It is a different design that can handle higher temperatures. To operate such hotends you require a little more experience as these hotends are a little less forgiving if you do not have the right slicer settings. Key parameters are hotend temperature, cold end cooling and retraction speed and length and amount of retractions in the model.

Another fact is that e.g. the Ultimaker cores concept (we opened a 0.4&nbsp;mm core to see that for ourselves) doesn't use a PTFE lining, nor do other brands. They can perfectly print PLA (even with a high retraction length). The only time if failed printing PETG (higher temp than PLA) was the result of a heat creep induced clog which was caused by a cooling fan failure (the cooling fan ingested something and seized up), so just one print of a few meters of the several kilometers 2.85&nbsp;mm that got printed.