Things do change during overclocking, because these mainboards overclocked the processor differently. The table below shows how far we managed to overclock our test processor and memory on different mainboards:
Gigabyte GA-Z77X-UP4 TH, which managed to overclock the CPU and memory to its maximum, is at the very top of the diagrams and often takes the leading position. However, even the Gigabyte GA-Z77X-UP5 TH mainboard, which fell a little behind it in overclocking, is also very often the leader in its group of boards that overclocked the CPU to 4.5 GHz. Moreover, In gaming tests Gigabyte GA-Z77X-UP5 TH does way better that expected. It even manages to outperform those mainboard models, which achieved better overclocking results.
Overall, we have every reason to conclude that both Gigabyte mainboards have no problems with performance of any kind. On the contrary, they demonstrate very good results that surpass our original expectations.