if the both cpu's are using 1600Mhz ram the performance just have a little difference but if the 7700k using 2400Mhz ram i think there's a huge difference , because APU's processor need higher clock ram
the processing power of the two yep its just clock speed but for the igpu its a different situation. its like the 7850k has r7 250 in it while the 7700 has r7 240 in it (not really but its just an overview of the difference in igpu speed)