Think its a mute point to worry about.
What happens when the KO cap fails or gets faulty ? send it in for repairs where as other makes you just replace.
A cap is definately advised as it keeps the esc running cooler and helps prevents voltage ripple/drop.
definately helps with punch too.
If you worried about looks then possibly look at chnaging the provided cap with a supercap that is slim. No matter which way you go you always have to juggle electronics to get a good fit.
Supercaps are available from Speedpassion and TOP Racing and maybe some other brands.
casterracing EX-1 Pro, SP Silver Arrow
TOP Racing Scythe, SP 17.5, SP GT Pro 2.0
TOP Racing Scythe, SP 4.5 V2, Hobbywing Xerun 120SD 2.0
TOP Racing Scythe, SP 13.5, Hobbywing Xerun 120SD 2.0