Really don't understand the difference, but do I want a coil/compressor with a TXV valve or fixed. Units we are looking at are 16 seer Amana Premium or Carrier Infinity heat pumps.
You want what the manufacturer calls for. I know Carrier will call for a TXV. At 16 SEER, I have a feeling Amana does too. Or you won't get the high efficiency and on a high SEER unit, could have some humidity issues as the TXV runs a colder coil.
TXV is the superior metering device. In addition to adjusting to changing temps - it keeps the refrigerant in place between cycles allowing it to pick up right back where it left off.
Are they more fragile than fixed? Yes. They can even be damaged during install.
Is it worth it? IMO yes.
Most newer units have gone to TXV. Haven't seen anything over 14 SEER that still uses fixed metering.
Thanks for the advice.