In terms of overall gaming performance, the Intel Core i5-3340M 2.7GHz is noticeably better than the Intel Core i7-4500U 2-Core 1.8GHz 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 Core i7-4500U 2-Core was released less than a year after the Core i5-3340M 2.7GHz, and so they are likely to have similar levels of support, and similarly optimized performance when running the latest games.
The Core i7-4500U 2-Core and the Core i5-3340M 2.7GHz both have 2 cores, and so are quite likely to struggle with the latest games, or at least bottleneck high-end graphics cards when running them. With a decent accompanying GPU, the Core i7-4500U 2-Core and the Core i5-3340M 2.7GHz may still be able to run slightly older games fairly effectively.
Both the Intel Core i7-4500U 2-Core 1.8GHz and the Intel Core i5-3340M 2.7GHz have the same number of threads. Both the Core i7-4500U 2-Core and the Core i5-3340M 2.7GHz use hyperthreading. The Core i7-4500U 2-Core has 2 logical threads per physical core and the Core i5-3340M 2.7GHz has 2.
Multiple threads are useful for improving the performance of multi-threaded applications. Additional cores and their accompanying thread will always be beneficial for multi-threaded applications. Hyperthreading will be beneficial for applications optimized for it, but it may slow others down. For games, the number of threads is largely irrelevant, as long as you have at least 2 cores (preferably 4), and hyperthreading can sometimes even hit performance.
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 Core i7-4500U 2-Core and Core i5-3340M 2.7GHz 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 Core i5-3340M 2.7GHz has a 0.9 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. In this case, however, the difference is probably a good indicator that the is superior.
Aside from the clock rate, the next-most important CPU features for PC game performance are L2 and L3 cache size. Faster than RAM, the more cache available, the more data that can be stored for lightning-fast retrieval. L1 Cache is not usually an issue anymore for gaming, with most high-end CPUs eking out about the same L1 performance, and L2 is more important than L3 - but L3 is still important if you want to reach the highest levels of performance. Bear in mind that although it is better to have a larger cache, the larger it is, the higher the latency, so a balance has to be struck.
The Core i7-4500U 2-Core and the Core i5-3340M 2.7GHz have the same L2 cache size, but the Core i7-4500U 2-Core has a 1 MB bigger L3 cache, so in this area, it wins out over the Core i5-3340M 2.7GHz.
The maximum Thermal Design Power is the power in Watts that the CPU will consume in the worst case scenario. The lithography is the semiconductor manufacturing technology being used to create the CPU - the smaller this is, the more transistors that can be fit into the CPU, and the closer the connections. For both the lithography and the TDP, it is the lower the better, because a lower number means a lower amount of power is necessary to run the CPU, and consequently a lower amount of heat is produced.
The Core i7-4500U 2-Core has a 20 Watt lower Maximum TDP than the Core i5-3340M 2.7GHz (though they were created with the same size 22 nm manufacturing technology). What this means is the Core i7-4500U 2-Core will consume slightly less power and consequently produce less heat, enabling more prolonged computational tasks with fewer adverse effects. This will lower your yearly electricity bill slightly, as well as prevent you from having to invest in extra cooling mechanisms (unless you overclock).
The Core i7-4500U 2-Core and the Core i5-3340M 2.7GHz both have an on-board GPU, which means that they will be capable of running basic graphics applications (i.e., games) without the need for a dedicated graphics card.
For an in-depth GPU comparison, click on the GPU comparison icon that you can find throughout Game-Debate:
On-board GPUs tend to be fairly awful in comparison to dedicated cards from the likes of AMD or Nvidia, but as they are built into the CPU, they also tend to be cheaper and require far less power to run (this makes them a good choice for laptops). We would recommend a dedicated card for running the latest games, but integrated GPUs are improving all the time and casual gamers may find less recent games perform perfectly acceptably.