There are many factors to consider when choosing between these two laptops. Of course, its obvious for a fact that the other is basically an upgrade, but let me explain further.
1. i7-4720HQ vs i7-6700HQ - they both offer similar clock speeds with a higher turbo boost of 3.6 for the 4720. the 4720hq wins with the single core performance benchmarks, but the 6700hq wins multicore tests. now don't get confused because their performance is basically on par with each other, but let me tell you that the 6700hq's technology makes it far more efficient in terms of energy use and temperatures. although they are on pretty much on par with performance, the 6700hq wins with its efficiency
2. DDR4 ram vs DDR3 - Hardly any noticeable difference here unless you're pretty particular with numbers, but generally, DDR4 ram offers higher bandwidth and offers faster multi-rendering speeds. One thing I could point out again is that DDR4 rams are more efficient than DDR3 with its lower voltages. Again, maybe this might not be so important to you. 🙂
3. Temperatures - this is an important thing to consider, especially with the GL551. most people who own gl551 laptops report or complain about thermal throttling at just below 75 degrees and would have lower performance right after. This is rather something negative as most laptops should be thermal throttling on at least 90 degrees or even 100. It's also all over the internet that ASUS technicians would admit to people that the gl551 model has a faulty sensor and such.
but on a positive note, a lot of people have also reported that updating the BIOS has increased the max temperatures for the laptop.
so on this factor, I guess the GL552 model wins again as it has less reported problems with its temperatures
4. SSD Upgradeability - Another important factor if you plan on upgrading to an SSD.
For the GL551 - PLEASE TAKE NOTE that the gl551 model only has ONE (1) drive bay for a conventional 2.5" SATA III SSD. But this is NOT an extra bay. You would have to take off and replace the stock HDD to put in the 2.5" SSD. But on another positive note, the model supports an Mini mSata SSD, but this would require you to open up certain parts of the computer (aside from its back panel) that could potentially void its warranty.
For the GL552 - The model supports and has an extra slot for m.2 2280 SATA III SSDs and is easily upgradeable through its back panel. Also, this will not void its warranty.
So again, the GL552 model wins this one
5. Screen - Both screens are IPS screens, but lets go to the PWM because you mentioned that.
Laptopmedia tested both laptop models (GL551jw-ds71 and GL552vw-dh71) and came up with these results. Note: Lower PWM is better
GL551 - NO PWM at all brightness levels.
GL552 - PWM is present at ALL brightness levels.
GL551 wins this as lower PWM would be healthier and less aggressive for your eyes
Going on to Color gamut, this is especially important if you're particular about colors with video editing, photo editing, modeling or rendering. Note: Higher is better
GL551 - 84% sRGB color gamut
GL552 - 91% sRGB color gamut
GL552 wins in this case
Now, if you ask me, I'll definitely get the GL552 model because of its efficiency with its newer 6th gen processor and DDR4 ram. Also to add is its easier upgradeability. But overall, they're basically almost the same and I guess the price would be the last factor you would think of.
