Traditional VC investment vs. bitcoin IPO
This is ultimately a question where you may have to choose between liquidity and control.  Traditional VC investments are a lot more liquid, in other words, they likely have a lot more money to offer, than any bitcoin stock market.  At the current exchange rate, the amount you'd like to raise is equivalent to roughly 15,000 bitcoins (on the 1.5 million end of the the range, anyway).  

Localbitcoins - you're a popular enough exchange that you may very well be able to raise that much in a bitcoin IPO.  

I imagine it'd be a lot easier with a traditional VC to make that kind of money though, and that would be in fiat already for the marketing efforts that you're planning.  But the catch is that the money the VC provides will likely have strings attached, they'll want some control of your business in return for that kind of money, or as you said, the 4 - 5 year exit plan.   

The other issue that you have to consider here is this: what are you looking for in return for this money?  Are you just thinking of the money going towards shares of stock, as in a bitcoin exchange?  Or do you want business advice for your business as well?  A bitcoin exchange can definitely provide liquidity, how much, I don't know.  But if you want business advice, then you are likely better off with a traditional VC since they will be able to provide that for you.