My pov, it is clear that the management give bigger focus on Stake than Primedice as we all can compare ourselves.
Starting from advertising, marketing, promotion, and some other things, Stake can be said as the priority one by the management.
Although there are still few hundred online players in daily basis at Primedice, but I think it wont last longer.
Coming up to speed of response by the support, it is understandable if Primedice is faster due to what is said by Mahdirakib.
Even at Stake, now 1 VIP host is handling more than 500 users (at least this number based on my own VIP host) so it is not surprising if the support is slower than Primedice.