I'll add to my previous that while I wear both muffs and plugs, if'n I had to choose one, I'd go with the muffs since even while they are more prone to interfere with the stock, they do offer:
a) better seal around the auditory sensors (ears)
b) they are easy to insert (especially if you have dry ears)and they don't tend to work their way out like plugs do and leave the ear with reduced protection.
One caveat though, and one I learned the hard way, avoid at any and all costs being close to or beside a muzzle brake with either or both muffs/plugs on. Muffs and plugs will reduce the noise level (dB). But they will transmit sufficient energy from the shock waves that result from the gas being ported out the sides of the brake into the ear canal (even if a muff/plug combo is worn). This can and will damage your hearing in some rather exquisite ways. The shooter is shielded from the gas for the most part but adjacent shooters, particularly when short barreled firearms/handguns are going off, tend to be in line for a lot of the gas blowout.