hey David,
I read the thread with interest.
If you're trading using margin trading (including options or futures) you are putting yourself at risk/disadvantage (that I'm not sure that you're aware of).
If we ignore the way that the brokerages operate then your leveraged positions can lead you to ruin really quite quickly.
With spot trading on the other hand it's harder for you to make 'good money' but there's less potential drawdown.
If you look at the exchanges, depending on where you are in the world, you should look at the top 10 exchanges (as was already mentioned).
The reason for this is that the top 10 exchanges will have the levels of liquidity that you need in order to ensure that you can always perform a buy and sell - without having to wait for a few hours (and risk slippage or non-execution of trades).
This is just my opinion but my background is trading across both retail and institutional markets.
I hope this helps,
Paul.