There are two ways in which and aerial installation can be carried out on your property, they are internally or externally. So, what are the benefits and does it matter? Well, to give an over view of an exterally fitted TV aerial, this is typically fitted to either a chimney or an outer wall usually high up. When an aerial is fitted to the chimney, the aerial head is attached to a steel or aluminum mast that is itself fixed to a bracket . This bracket is fixed either by lashing cable or by being bolted to the chimney stack. The coax cable that is connected to the aerial head then runs down the roof over or under the gutter and down the wall into the room through a hole that has been drilled. This kind of set up when done right will last for many years even many decades, however, it is subject to the ravages of the worst of the UK weather and because of this the aerial system can become compromised and fail.
One of the most common faults that occur with externally fitted aerials is either that they get water ingress both in the aerial head and or the coax cable coming from the aerials head, or they get damaged and even come down from there fixings due to strong winds. When either of these things happen to the aerial system it is then time for a replacement as repairing them after water ingress is impossible and most times if damaged in the wind ther is little that can be done to repair them.
The benefits of having the TV aerial fitted outside is that it will receive a much strong and clearer signal than if it was fitted within the loft or attic space. In some cases an aerial fitted in a loft can receive up to 50% less of the signal opposed to being fitted outside. If the house is located in an area where the signal is not too strong, then it would be preferable to fit the aerial to the tallest part of the house on the outside to give the aerial the best chance of picking up the strongest signal available.
The benefits of having the aerial installation in the loft are that it will never succumb to the weather and therefore will last for decades without it failing. If there is enough of a quality signal picked up when in the loft it is a good idea to have it installed there. Although the coax cable may need to be run externally, this is where the cable runs from within the loft out and down the external walls and then into the property. Secondly, it is aesthetically pleasing for the aerial to be out of sight and by fitting them in the loft will hide away the unsightly aerial system.
Unless you are a good DIYer I would always suggest calling up an aerial fitter to carry out any aerial installation. This is because it is in its nature a dangerous task to undertake, unless it is being carried out on a bungalow. So the recommend is if possible have the aerial installed in the loft but which ever you decide I would always recommend using a decent aerial fitter.