Well let's see ...,
All HB DI units (regardless of Gen) have a dedicated DI piezo ...
HELIX MEGA SI units also have a dedicated DI piezo ...
HELIX 5 SI G1, HELIX 7 SI G1, HELIX 5 SI G2, HELIX 7 SI G2, HELIX 7 SI G2N - none have a dedicated DI piezo ...
Any unit with a dedicated DI piezo will have better DI than the SI units that do not have a dedicated DI piezo ...
(ONIX and SOLIX also have a dedicated DI piezo) ...
Rickie