I just joined these forums but have been messing around with alt-coins for about a month now. When I first started
I wondered what the difference between all these coins was and which coin to mine/trade if any. Other than
evaluating each coin on its merits (make sure its not a scam) a good measure of what to mine/trade can be found
by looking at how active it is on an exchange. My exchange of choice because it has the most pairs is Cryptsy.
At the following link you can find a table of coins traded on Cryptsy, sorted in descending order by USD value traded in last 24 hours.
I used the current price of BTC on BTC-e ($740) for that conversion.
As you can see the DOGE, LTC, WDC, QRK & PTS are the most actively traded BTC pairs.
Here:
https://docs.google.com/spreadsheet/pub?key=0AnTvbCwD-jbKdDB0UlhkeXlfTWtNdGVOVTVsaEo5TGc&single=true&gid=1&output=htmlNOTE: This table only lists BTC pairs and not LTC or XPM pairs. I may do those later.
I hope you have found this information useful.