In the US, the best option is Coinbase or LBC. Coinbase has lower fees, but it's around 4 days from the time you execute the buy order until you receive your btc. You can also throw privacy out the window. Not only do you have to provide ID and verify address, all transactions will show up in your back statement, clearly saying "COINBASE". If you have large volumes, you're at risk of getting your bank account closed (possibly banned), even though coinbase itself fully complies with AML/KYC.
LBC is fairly anonymous as the buyer. The trade off is higher fees, but at least your keep your purchases off the radar so you don't have to worry about filing taxes and such. You get it nearly instantly, depending on if you're able to follow instructions from each individual seller.
LakeBTC, it comply with U.S. laws, and cheaper compared to Coinbase
LakeBTC is nowhere near as established as coinbase. Many smaller exchanges have come and go, so this is the risk of having transactions with a smaller exchange. I've been personally affected by TradeHill going underwater back in the days. Still can't recover my btc back from Jared.