The purpose of a resonator [a hollowed out chamber] in the path of an exhaust system is to dampen the noise from the engine that ultimately makes its way thru the exhaust [sound], without robbing the vehicle of power.
Certain sound frequencies - though that should not - do make their way thru the muffler. These frequencies can create drone and general annoyance for the cabin occupants. This is where the resonator comes into effect.... or is supposed to. It's the last line of defense to grab those frequencies and eliminate them prior to the final exit at the pipes [i.e.: what you hear]
All things equal, a resonators distance from the exhaust's muffler is more vital than the actual resonator itself [size, shape, etc.]. It's usually placed by vehicle manufacturers a certain distance from the muffler to best affect its use based on the vehicle/engine combination.
Removing resonators can be a risky thing as these annoying sounds and drones can ultimately make their way to your hearing. More often than not, removing the OEM resonators [without removing anything else] may induce drone that was not there prior. So yes, it's a gamble.
However, if a high quality aftermarket exhaust system [pipes and muffler combo] comes without resonators, or calls for resonators being deleted, and then nine times out of ten drone is NOT an issue. This is because these aftermarket exhaust manufacturers have extensively tested these units prior to making them available to the consumer to rid them of any drone or "resonating" sounds that will disturb the cabin occupants.
My Magnaflow 16869 catback exhaust with the Magnaflow 10778 Y-pipe is an excellent example. Absolutely no drone anytime.
Just to add finally, I highly do NOT recommend removing resonators for those people who choose to do ONLY a muffler change/upgrade. This is because - contrary to what people will tell you - OEM piping, mufflers and resonators work in conjunction with each other to rid the cabin of drone and any other annoying sounds. Eliminating the resonators from an OEM exhaust system, with JUST a muffler upgrade, will almost ALWAYS induce unwanted exhaust drone.
Hope this helped some.
Good luck ultimately in your decision.