In terms of overall gaming performance, the Intel Pentium J2900 2.41GHz is noticeably better than the Intel Pentium Dual Core E5400 2.7GHz when it comes to running the latest games. This also means it will be less likely to bottleneck more powerful GPUs, allowing them to achieve more of their gaming performance potential. The Pentium J2900 2.41GHz was released over three years more recently than the Pentium Dual Core, and so the Pentium J2900 2.41GHz is likely to have far better levels of support, and will be much more optimized and ultimately superior to the Pentium Dual Core when running the latest games. The Pentium J2900 2.41GHz has 2 more cores than the Pentium Dual Core. With 4 cores, the Pentium J2900 2.41GHz is much less likely to struggle with the latest games, or bottleneck high-end graphics cards when running them. More important for gaming than the number of cores and threads is the clock rate.
Problematically, unless the two CPUs are from the same family, this can only serve as a general guide and nothing like an exact comparison, because the clock cycles per instruction (CPI) will vary so much. The Pentium J2900 2.41GHz and Pentium Dual Core are not from the same family of CPUs, so their clock speeds are by no means directly comparable. Bear in mind, then, that while the Pentium Dual Core has a 0.29 GHz faster frequency, this is not always an indicator that it will be superior in performance, despite frequency being crucial when trying to avoid GPU bottlenecking. As such, we need to look elsewhere for more reliable comparisons. Aside from the clock rate, the next-most important CPU features for PC game performance are L2 and L3 cache size.