Concur with Nick, I'll land with brakes off (but toes on the brakes, just in case..) nearly all the time. Also, nose wheel/tail wheel lock in, regardless of whether the brakes are on or off, to give directional stability when the collective is dumped. I've seen a Sea King rotate about 25 degrees, when the tail wheel lock was out, and it's not a pretty sight. Just as important on start up, as well. If it's a pitching or moving deck, or an offshore platform, local requirements come to the fore. Company regs (eg North Sea quoted before), Squadron SOP's, etc will dictate what has been learnt the hard way by others, and saves a lot of relearning. Odd points to consider are deck size and surface; if there's a net made of large diameter rope, you may be advised to leave the brake off, to allow the tyres to roll off the rope and into a hole. Some S76 landings, when the torsion bar between the mains push the other wheel down, need a bit of movement in the wheels which would not be there if the brakes were on.
HFrog, Whirlwinds with brakes. What will they think of next
Matthew, Was your load internal, and if so, wasn't it an option to sling the things? I'll bite, my guess is that the brakes off would allow some rotation of the wheels, thus reducing the suction/stiction of the gear stuck in the mud, thus allowing a better chance of coming out of the gloop.