Minimum packet size Ethernet requires 1.488 Mpps per gig for wire rate. The 2960G-24TC-L has 24 gig ports, so 24 * 1.488 = 35.712 Mpps. The 48 port would require double that, but likely the forwarding hardware (likely the same for both switches) tops out at 39 Mbps.
BTW, both switches have a 32 Gbps fabric, but require 48 and 96 Gbps, respectively, for non-oversubscription. Also, PPS required performance drops with increased packet size, so for larger packets, fabric bandwidth could be the bottleneck on either switch.
