"gaming" doesn't really mean anything.
if you mean mechanical keyboards, they are essentially made of 1) a pcb 2) a shell 3) key switches.
for the pcb, they are practically all identical; they nearly all feature NKRO, are all inderstructable, some might have additional features such as media keys. for the shell, as long as you are paying a regular mech price (around $70 or over) you will again get pretty much the same quality in all products.
i have heard complaints about corsair's kb range, and i have also heard many people saying they work fine. probably just a case of volume, since they are some of the most common kb around, you gonna hear more complaints about them.
the switches are again, almost all cherry. which means that more or less whatever brand you buy, you are getting the same keyboard.
so, what makes the difference is the deviations from the norm. a few mech kbs have non-cherry switches, such as topre, or kailh.
if you want a particular feel, then you might want to select your kb based on what switch it uses.
if you want a backlit kb, you will need one which has ABS keycaps; backlit PBT keycaps do not exist on the market - save for one particular case of a mass-buy on multidrop, which were custom made.
if you want a tenkeyless format, or a media keys format, that again will limit your choices.
once you have decided what you want, there is little difference between which one you get. a cherry switch on any pcb feels exactly like any other.
regarding the customer service, it's really irrelevant - you can use a mechanical keyboard as a blunt instrument to bludgeon to death a home intruder, and then type the 911 call on your pc afterwards.