What will be your next firearm and why?
FN FAL .308, because FN makes quality products and I need a large caliber weapon for long distance.
I live 200 km from the FN-factory. I have no guns. What FN gun should I buy to protect my house.
I live alone, and there are no children.
The most important consideration is what can legally own and practice with. An illegal weapon that you have to keep in the roof or under the floor boards does no good.
Second consideration is ammunition availability..
Defence in an urban situation calls for stopping power without overpenetration. A rifle is no good because the rounds will go straight through a human torso and the walls of the house next door, too. Get a repeating shotgun. A pump or slide action is best. If they're not legal in your country get a doble barrel. Just have a barrel/s less than 500mm (20 inches).
For more serious emergencies and in rural areas the rifle is better suited. If a semi-auto battle rifle like the FAL or FNC/M16 etc are not legally obtainable, get a bolt action sporting rifle with good iron sights or a low magnification telescope (no mre than 2.5x magnification). This will allow you to engage close in targets more quickly. Get the rile in a military/police caliber if you can, ie; 7.62x51mm NATO (.308 Winchester), 5.56x45mm NATO (.223 remington).
BTW, surplus WW2 era military bolt actions like the German Mauser Kar98k, the Chech CZ 24, Swedish Type 38, Swiss k31, French MAS36 or the Soviet Nagant 44 carbine are cheap to buy, very rugged/durable and accurate. They have good, practical battle sights and reload very quickly with stripper clips.
Check out the CZ line of sporting rifles from the Check Republic. They are well made and have good iron sights.
A high capacity, compact 14+ shot pistol like the FN/Browning High Power , Glock 19 or CZ 75 in 9mm NATO is very handy, too.