Question: My lease is up this summer and I'm planning on moving apartments. The problem is that I also have a 3-day trip scheduled to start the day my lease ends (cannot be changed).

My cat will be a little over a year old at that point and has always lived indoors at my current apartment. When I go on trips, I usually have a cat-sitter come to the apartment. I've only boarded her once, just for the day, and she took a few hours to return to normal after coming home.

I'm concerned about her reaction to moving to a strange new place, especially if I were to leave immediately after. What is the least bad option for her?

1. Move a week or so early, leave her there and go on trip (avoids boarding, but is that enough time for her to get used to it?)
2. Board her, move, go on the trip, and bring her back to the new apartment afterwards (or would that be doubly traumatic?)

Answer: 
I would move a week early. Going to a new place is traumatic for most cats, they need time to adjust and scent mark. As you said, boarding then new apartment would be doubly traumatic. 

If there is not enough time to get used to her to get used to the apartment, why would it be any better with boarding? In a boarding situation, there will be all sorts of other cats and stimuli to stress her out. In your new home, she can feel relatively safe hiding under **her** bed :) 

Even if she has been boarded there before, it is unlikely that she will occupy the same domicile with her own scent.
I did the exact same thing once, I moved out to a new apartment with my cat and there was an emergency at the day I was moving so I had to leave for a couple of days.

What I did was; I confined her to a smaller room full of her favourite things & furnitures. This included my bed (she always sleeps with me), her toy collection, her favourite blanket which she sometimes kneads and cleans, a couple of my clothing, food, water and of course a closed litter box. Since she was surrounded with familiar things & scents she had an easier time to adjust (which I have heard from my friends who kept an eye on her basic needs a couple minutes each day). And when I returned she was pretty much normal but I had to go through the skittish behaviour when I introduced her to the rest of the apartment.

If you can bring her a week early; by all means do it. Your cat will probably adjust in that time frame.