A Japanese usage question

[stormdog]

I'm working through a section on asking and answering questions about where things are. A few examples, put next to each other, confuse me a little bit. mikazo and cranberrynomiko, since you've been kind enough to offer input before, I'd be very grateful for your comments if you have some time.

(I should have mentioned samiitiger in this post too since she knows some にほんご too. I was pretty tired last night. Sorry!)

ちゅうしゃじょう　は　どこ　に　あります　か。
chūshajō wa doko ni arimasu ka.
parking lot (subject) where (location) to be/exist[inanimate object] (question marker)
Where's the parking lot?

スミスーさん　は　どこ　に　います　か。
sumisu-san wa doko ni imasu ka.
Mr. Smith (subject) where (location) to be/exist[animate object] (question marker)
Where's Mr. Smith?

ビール　は　どこ　です　か。
bīru wa doko desu ka.
beer (subject) where to be/exist (question marker)
Where's the beer?

What puzzles me about those is the difference between [noun] wa 'doko ni arimasu/imasu' and [noun] wa 'desu'. I'm not quite sure why some sentences get the more complex construction with the location marker 'ni' and the imasu/arimasu verbs, and other sentences get the basic 'desu' verb with no location marker. Is one just less formal? I thought maybe it was the difference between talking about people versus talking about things, but as above, there are examples of both forms when talking about things.

Still having so much fun with this, even if I am worried about being behind after missing two classes.