I'll preface this by saying, I'm not planning to do either of these things, I'm just bored and thought a theory discussion might be interesting. I definitely don't have $2k to spare
So if you had $2k-$2.5k to invest in Bitcoins which would be more profitable?
Use the money to purchase as many Bitcoins as possible. Right now the current price is $16-$17ish per coin, and for discussion sake, we could say you would have up to a month to purchase them, in case you think the price will lower in the short term. The advantage to this technique, in my opinion, is that you would essentially be starting at your initial investment. Of course it's possible the Bit Coin could crash, but we all hope thats very unlikely.
Invest the money into buying a solid GPU and attempt to mine Bitcoins. Mining has gotten ever more difficult recently, and unlike option 1, you are "starting behind" in that you would need to earn $2k worth of bitcoins to get back to where you started. At the same time, you are still at the mercy of Bitcoin value.
In my opinon, Option 1 seems to be more profitable today, but I really have no idea where the value of the Bitcoin will be anywhere in future, so I was wondering what everyone else thinks?