The biggest issue in proto3 is the missing "has_<field>" functions (e.g no distinction between a field's default value, and a special <missing> state). There a

The biggest issue in proto3 is the missing "has_<field>" functions (e.g no distinction between a field's default value, and a special <missing> state). There are suggested workarounds for this, but I'd just stick with proto2 for the time being as proto3 is still WIP.