Missouri is now Castle Doctrine so I suppose #1 in most situations would be justified. However;
I am not pre-programed to just fire automatically.
There may be situations where I would be compelled to choose #1, but most often I'm thinking more along the lines of choosing #2, for a variety of reasons.
A) (and not the least of which) I am not blood thirsty looking for the first opportunity to legally shoot someone.
B) I am trained in, and fairly proficient in, close quarters combat (armed & unarmed), weapon retention & disarming techniques and handling armed subjects so I feel a bit more confident in my tactical skills than someone like my wife or many other folks.
C) I like to be able to make a positive ID on someone before I shoot, using the element of surprise and a blinding tactical light like my Surefire or my Glock mounted Insight M3. (for some reason Mr. Murphy likes to ride shotgun in my ride and I don't like the sickening thought of accidentally shooting any friendlies, no matter how remote the chance.)
D) I like the idea of if I do have to shoot him, I like the idea of it being in the front with him facing me as opposed to being shot in the back. (yeah, I know... shooting in the back can at times be effectively explained and defendable in court... but again, Murphy likes being my co-pilot, and why go down that road, if I don't need to!)
Now, in the original post, I see the Intruder and he hasn't seen me... So, before I illuminate him and give a commanding verbal challenge... I am going to take up a position of tactical advantage with a wall against my back so I can't be out flanked by a commrade of his and observe him for a second to get my bearings and see what's what!
If, while his back was to me, I could obviously see a weapon in his hand... I would absolutely open fire without hesitation and without a warning.
Other than that, I would probably challenge him to freeze and shoot if he failed to obey commands. Then order him to the ground, and again shoot if he failed to obey commands.
Now my wife on the other hand... Will not engage in conversation and if she is home alone and finds an intruder in the house, she will shoot without warning! Her situation and circumstances are totally different than mine.
The main caveat as in all situations... I play it as I see it! Nothing is set in stone and all those types of encounters are very fluid in nature.
The Castle Doctrine law in Missouri is unchallenged in court so far and as far as I'm concerned, it is only a minor safety stop for the citizens. (looks good in theory, but in practice... has yet to be proven out!) To me, it still is not a license to blast away without the possibility of some consequences I may not have thought of yet. And I certainly don't want to be a "test case!"
JMHO... YMMV