Closet- good option for less picky plants. people will think you grow weed, though
Window- for even less picky plants then the closet, yet they will be visible to the world
Tank- grow anything, but space is an issue. use this if you plan to buy expensive plants.
my advice is to use both windows and a tank. when you order a plant, put it in the tank for a week or three, and then move it to a window if you so choose. if it declines, move it back to the tank. i do this, and it works rather well. my expensive plants stay in the tank but most of my nepenthenes are either in windows or in my bog garden.
the best advice i can give for a tank is the dimensions, when picking one out, remember height is least important. the longer and the deeper the better! and trust me, if you get into CPs it WILL fill up fast. spend the money on a big tank now so you dont end up replacing a small one later.