The disadvantages are:

Although easy to set, it is tricky to install in a mole run, particularly in deep ones. It has to be covered in such a way that nothing (e.g. stones or bits of turf) fouls the moving parts. Because of the sticking up handles, it is difficult to cover totally so as to wholly exclude the light from the mole run without impeding the action of the trap..

• A stone in the wrong place will jam the jaws, a frequent occurrence in stony soils.
• If there is a frost, the soil round the handles freezes and prevents the trap from working.
• Heavy rain will wash the soil from over the trap into the run thus exposing it.
• It is not easy to install in a very shallow run, nor a very deep run.
• In my view it isn’t a particularly humane trap, as the spring is not very powerful.
• It can’t be used with livestock present, owing to the sticking up handles.
• Hitting the trap with a mower will probably destroy the trap and damage the blade of the mower. 
• There are quite a number of badly designed copies on the market.

All these factors contribute to a much higher level of misses, i.e. a mole that has passed through the trap and either triggered it without getting caught, or dug under it, or even worse been partially trapped and then escaped. You then more often than not have a trap shy mole. I used to think I was doing well if 50% of scissor traps which a mole had passed had a dead one in it. With the Tunnel trap that figure is over 80%.

Why then is this the most common trap available? I think because of its simplicity in setting and the sturdy design. The only real alternative, the tunnel trap, is quite tricky to set until you get used to it. There are many different brands on the market, and few, if any, have maker’s names on them. Some of the foreign imports are poorly made. As I am not a user of this type of trap I am unable to comment on the different brands although I guess you get what you pay for. However if you prefer to use a scissor type trap then I strongly  recommend you look at the Talpex Trap below.

THE TUNNEL OR DUFFUS TRAP

To me, logic dictates that this is the perfect design of trap. It has a powerful action, incorporates a half tunnel, so is dead easy to cover, and the working parts are not prone to being jammed by stones, turf etc. Be warned though that one of the most popular brands on the market has a design fault and although it will catch moles, the catching percentage is lower than other brands. Many other of the cheap imports are equally bad.

Advantages of the Tunnel Trap

It is easy to install in a mole run as the half tunnel means you can just brush a bit of loose soil over the top and all light is excluded from the run.

• Fast powerful killing action.
• Easy to “tune” the trap so that it is very sensitive to being triggered.
• Working parts virtually never jammed by stones or turf.
• If covered by a piece of turf or a small board, will not be affected by frost, or heavy rain.
• It can be set in a paddock/field containing  livestock  if covered by a small board.
• It will not damage a mower as no part of the trap is above ground (except in v shallow runs).
• If trapping on a lawn, it is much neater than a scissor trap. Cut out a piece of turf above the run with a border spade which is the same width as the trap. The turf can then be replaced when the mole has been dealt with, the molehills removed and the lawn will be undamaged. 
• It can be used equally successfully in deep or surface runs.
• It can, and occasionally does, catch two moles at a time.
• It is easy to conceal when set in places where the public have access, and so is less likely to get stolen.

Disadvantages of the Tunnel Trap

• They can be tricky to set unless you are shown the technique. Get the setting wrong and you can get a painful rap on the fingers!
• As sold most are not suitable for installation in a run.  The trap needs to be “tuned” so that it triggers quite easily. It is simple to do once you have been shown or seen how to do it.
• You cannot see from a distance if they have been sprung.
• As nothing shows above ground, it is easy to lose a trap if a child/dog/etc removes the marker stick.
• The best of these traps is manufactured in England, and, after tweaks to the design over the years, now work “out of the box”.

TALPEX  TRAP

If for some reason you prefer to use a scissor type trap rather than a tunnel, then I highly recommend this one. It is very effective, particularly on moles that are proving difficult to catch, and is much used on mainland Europe. The original Talpex comes with the word Talpex on the trigger plate and is made in the Netherlands. There are lots of copies around and some of them are terrible.

Advantages

• The trigger mechanism on this trap works in a different way from the above two traps. Instead of the mole having to push with flipper or nose, it is the action of pushing soil to restore the tunnel that triggers the trap. It is therefore very useful if you get a trap shy mole that consistently plugs a tunnel trap, which does occasionally happen.
• It’s a very powerful trap, which can make it a little awkward to set until you are shown how. You do not set it by squeezing the handles which is the obvious but almost impossible way. Do not buy the version with setting handles on top as they are not necessary.
• It needs no adjustment before use, except to bend the trigger plate downwards and very occasionally to file any small burrs off the pin.
• It is relatively easy to install in a mole run, but takes a bit of time especially if working in stony ground.

Disadvantages

• The main disadvantage of this trap is that, like the scissor trap, you can end up with  stones in the jaws. In stone free soil it is quite excellent.
• Unless you know how to install one, then you may get a high percentage of moles passing through. without triggering. I am not giving away all my secrets, so to learn that particular skill you will need to buy the Manual!
• It is not good on shallow surface runs.