I have 4 different Luger P08 pistols - they come in a wide variety of configurations - different calibers, different barrel lengths, etc. In general, I would not recommend them as a personal defense weapon. The only real advantage of them is that the majority are chambered in 9x19 which is the most common pistol caliber. Beyond that they are not very practical. Most of the older "shooters" that are floating around are a mish-mash of spare parts that were carried out of Europe over the last century by either returning soldiers or by import companies. If they don't have matching serial numbers across all the parts they are worth almost nothing (few hundred $ at most). If all matching numbers, then they are more for collecting and not shooting. I have two relatively rare collectibles and two "shooters". Both of the shooters tend to fall apart after firing a dozen or so rounds. (being old the tolerances are sloppy and the side plate that holds them together tends to fall off - you can see a lot of references to this problem online).
So bottom line, they are neat pistols, but I would not consider them "practical" for defensive purposes - they are ungainly, not particularly accurate, old, and they are HEAVY as compared to a modern 9mm.