Archer C64 and Archer C6. I am confused between two.

It's my first time buying a router. Before this I have an ISP provided router.
My use cases are like these:
3 android phones - out of which 2 are with 5Ghz and one with 2.4Ghz. 1 computer with ethernet 1 Gigabit, 1 homeserver/nas/tinkering computer with 1 Gigabit, some others accessories.

My ISP plan is 100mbps.

Why I am confused?

I am worried that bcz of small form factor of C64, it would get hot quickly.
I don't about the number of cores for both. Only know that one comes with 1.2Ghz CPU and other one with 880Mhz(.88Ghz).

Somewhere I found that C64 is weak in security compared to the C6. 

C64 is newer so I am willing to buy it, but when I read reviews, it says that it has less features than C6. Such as no separate guest network for each band, no Onemesh support.