8550U is a low power quad core/8thread cpu with a base operating frequency of 1.8Ghz Turbo up to 4Ghz
7700Hq is older but also is 4core/8thread with a base frequency of 2.8Ghz, & Turbo to 3.8Ghz.
Both use Turbo Boost 2.0 technology which depends on several factors as to what you get. Typically if all 4 cores are active you pretty much run at base frequency giving the 7700 quite an advantage - 1000Mhz. In apps that use single cores, the 8550 has a 200Mhz advantage which is all but unnoticeable in anything but a benchmark.
And... Matlab is multi-threaded so it will use the entire 4c/8t of the cpu
Enjoy the 7700!
I also believe that the 8550u, being a low power cpu will have a thinner designed cooler and probably be constrained to lower speeds by Turboboost which also evaluates the temperature of the cpu when deciding what speed to run at.