Replacing ground loop heat pump

Hello all: Thanks in advance for any advice you may give.
I live in northeast Georgia, near Athens. Hot summers (90-100 late June through August, mild winters - coldest was 6 below, but usually teens to 30s from late November through mid-March).
I have two 15 year old 1.5 ton Florida Heat Pump water source heat pump systems on a closed horizontal loop. One is a split system, the other is not. One has failed completely, and the other has had lots of repairs and is again in need of a cash infusion. The entire system was installed by certified professionals with plenty of experience with water sourced systems.
I'm ready to replace one, maybe both. We don't plan on moving...ever...
Has this technology become more reilable (duh, I know this is a dumb question, but I don't want to purchase the same problems and suffer another 15 years of repairs, and heating/cooling bills that were/will be higher than expected)?
Does the loop material wear out or degrade (thick walled black plastic pipe 4-6 feet underground)?
Should I consider air sourced heat pumps, or replace with another water sourced?
I've been told to not purchase the highest efficiency systems as they are more prone to need repairs (don't get the lowest cost "contractor grade" systems either).
Also I've been told to keep it simple (no zoned system with dampers, etc. as these too tend to need more frequent repairs).
Any suggestions on whether to add a "hot water recovery" system for heating household water in the warmer months?
Any comments or suggestions on air to air versus ground loop and brand reliability (i.e., Trane, WaterFurnace, FHP, Climate Master, etc.) would be appreciated.
Thanks again
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