Whether market is rising or falling does not matter...
I can't quite agree with that statement. In a falling market by the time I get to sell my coins, the price may have already down lower than my buying price. When the trend is upward, the risk is a lot less then.
Yes, but what if you're buying? Then the opposite is true. Arbitrage is looking at the price difference across different exchanges, regardless of market movement. For example, right now, because of recent crackdowns in India and Pakistan, Bitcoin price there is about $1,000 lower than the global average (because there's less demand, and added risk). So, whether you buy or sell, prices there are lower. In this case, arbitraging would seek to Buy from Pakistan and sell globally.
Conversely, where prices are higher, like in Zimbabwe, arbitraging seeks to buy globally and sell in Zimbabwe.
