When we first started our trapping service, we extensively field-tested virtually every mole trap on the market to determine which one produced the best results. Regardless of cost, soil composition, time of year, type of tunneling, or scope of the mole problem, we discovered that the Victor Out O' Sight Mole Trap always outperformed its competitors (a conclusion also reached by the overwhelming majority of professional mole trappers in North America, by the way).
We can go on and on and on about why this trap's design is the best, but here it is in nutshell. Every mole trap has a "sweet spot" or a particular tunnel depth that maximizes the trap's operation. As you know from looking at your yard, moles construct tunnels at different depths. If the placement depth of the mole trap cannot be adjusted relative to the depth of the mole's tunnel (i.e. if you can't set the trap into the ground), the trap is very limited in its effectiveness. This is why "surface traps" that are restricted to use on top of the ground consistently fail.
Surface traps include the Easy-Set Mole Eliminator, the Nash Choker Loop, and the most common mole trap of all, the Victor Plunger or Spear. Catching moles consistently with a surface trap is as unlikely as hitting fastballs consistently while restricting your swing to only one level of the strike zone.
Interestingly, the shallow tunnels where surface traps are effective are also the tunnels that moles travel the least! Moles pre-construct tunnels which they then re-travel in their search for food (as opposed to digging and eating and digging and eating). Their prey species, principally earthworms, are concentrated at different depths depending on the weather and soil conditions (hot, cold, and dry conditions in particular drive prey deeper into the ground).
The tunnels that are constructed even a few inches into the soil consequently produce food more consistently than the shallowest tunnels. Not surprisingly, moles travel these deeper tunnels with the greatest frequency year-round and are the best places to set traps. This is particularly true in established mole territories.