Our Bristol/Bath French sessions are based round pipes and gurdies in D/G and G/C and this has shaped my box choices and playing.
So for major tunes I use my DG two row for D and G, and my CF for C
For Minor Tunes in G, D and I use my CF 3 row. using (DG-speak) A minor and E minor fingerings.
I'm working on learning to play in C minor, using (DG-speak) D minor fingering with Ds on the draw.
A GC box does give you Dminor easily on the inside row, but the A minor on the outside row would be less useful for me as the pipes and gurdy never play in that key. A GC box with G reversals on the 3rd row would helpfully give you G minor on the draw.
In speaking up for CF, I'm also influenced by the fact that Andy C who plays with gurdy in Blowzabella, has always carried around his DG and CF Morys; and Fred Paris carries around his GC and CF Hascys. And Stephane Milleret regards his CF centering on the D tonality, as his main instrument, with the GC box as the extra.