Hollow Tine Aerators - use hollow tubes of metal to remove a plug or core of soil, leaving a hole and leaving the plugs on the surface.
Spiked Aerators - these use spiked wheels to leave holes in the ground by piercing holes, deep into the soil.
Some experts think hollow tines are better and some extol the virtues of spikes.
Hollow Tines - leave plugs of earth on your lawn, which you may want to remove, but many feel that the holes left are more efficient for aeration. Hollow Tines are considered to be best for easily compacted, clay type soils.
Spikes - are neat and leave no plugs of earth, but some gardeners think they compact the soil rather than leaving holes. They are considered to be ideal for for loamy soils.
In fact, when it really comes down to it, both styles of aerator will do the job. Both improve drainage and let air, water and nutrients in to the soil, and release carbon di-oxide, improving the lawn’s chances of growing healthily. The rest is entirely a matter of taste and preference, though, as suggested above, the soil type of your garden or grounds may affect your choice.