Gold pins cost more... that's all.
I would honestly recommend *anything* other than JJs for the preamp in that amp - it's already and extremely dark/midrangy, borderline muddy/harsh amp (especially on the lead channel), and JJs will make it more so and then some. That's not a put-down to the amp, I used a DC-5 for many years and liked it a lot, but it really does need the mids keeping under control, and the DC-3 does even more. JJ power tubes aren't so bad, and they will at least hold up well in it.
Surprisingly, the standard Mesa Chinese 12AX7s sound pretty good in it if you don't want to go to NOS or try finding some good used old tubes. I would also try a couple of 12AT7s in it, in V5 (reverb) and V6 (phase inverter), they will soften and deepen the tone and increase clarity. I did this for a friend's DC-3 and it made it a much more versatile-sounding amp.
