While I can think of a bajillionty reasons why the imagination room would be insanely awesome and fulfill many insanely fantastic fantasies of Epicness that are just flat out impossible in real life, I'd have to go with the money.
If I cannot take anyone with me, then I'm not going to leave my girlfriend ( @Arylett Dawnsborough) behind. If I could take her with me, then the imagination room would certainly be the way to go. You might think "Oh, but you can just make a copy of her in the room!"
That's fine and dandy, but I would have the thought in my mind that I left her all alone in the real world without me. She would think I just disappeared, left her without any warning or possibly even died. I would have that thought in my mind constantly during my time in that room, and I imagine it would turn itself into a nightmare. I'd probably lose control of my own emotions and turn my own super imagination room against myself. And to be honest, I'd totally deserve it for abandoning Arylett like that.
A hundred thousand dollars on the other hand? I can use that to make the both of us happy for a very long time, and I wouldn't have to worry about my thoughts quite literally trying to kill me. :3