I believe the black HGs are the same as the M71. Valmets system was fairly interchangeable.
I'd keep the black HG, as a change in furniture is a nice option!!!
I personally think that guns that have "NICE" wood have an original nostalgic look that the new black era of guns are missing. The M78 is an older era SAW/LMG. As such I think the wood is better.
Being able to put on the black HG with another black AK stock would also have a modern ### appeal also though.
If you were going to do some serious shooting with it I'd use the black gear. For occasional shooting and show and tell, use the wood.
Either way you will be happy..... just depends on your mood.
I don't think that the carry handle matters. It is a little touch that seems nice but is not actually that functional.
If Valmets ever get deprohibited...... get an M71 and get a Galil folding stock.... it'll look great & shoot great - have a black rifle look and are the cheepest Valmet going!!!!