I've only done The Dig myself, but from what I've heard they are all amazing. I'd go with whatever theme sounds most interesting and you shouldn't regret it. When we did The Dig it felt really immersive and I'm sure all of them will have that immersion present.
You'll most certainly enjoy the Apartment. We had a really good time. With enough time and deciphering skills it can definitely be done. Haven't tried the Dig... BUT the Apartment is a great choice. It was 9 of us and it worked. It's the size of a studio apartment. You'll enjoy it for sure.
I have yet to find an escape room that I didn't like. I've only done the Clocktower at Escape the Room and it was enjoyable. I would recommend a group around 4-6 people for it. We had 9 and it felt a little crowded with not enough things for everyone. If I went back I think I'd try the Dig.
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