Have tried both, extensively.
I’ve had Mallets and Candys, the latter was lethal with my Spesh SPD shoes as there was no grip at all when unclipped, especially if wet. The Candys came off my bike very quickly after I almost ended up under the wheels of a lorry thanks to slippage and vague clipping-inness.
The Mallets have been a mixed bag, the first pair disintegrated halfway through a day out in Epping Forest. The second and third lasted the distance but the clip mechanisms began to feel noticeably baggy over time. Although rebuilds are a doddle, the wear rate of the cleats makes them a yearly purchase which proved an annoyance with three bikes.
I replaced them with plain old Deore Trail on my hardtail, XT Trail on my XC bike and DX on my AM bike. It’s been three years now and the Shimano stuff just keeps on going with minimal effort. Clipping in is much more positive and adjustable too, at the expense of float. Cleats are made of steel and just last and last. When running unclipped, the small platform cage of the Trail pedals are surprisingly effective.
BTW, I have two sets of Mallet Mk1 pedals looking for a good home if anyone is interested?