Thunderbolt,
Typically, on average, how long does it take to execute a trade in a somewhat volatile stock? My current online broker does it in about 10 seconds -- would upgrading to an EDAT be cost efficient?
If I used an online broker I wouldn't trade somewhat volatile stocks! And I'm assuming you're talking about market orders? If so, both Realtick and CyberTrader take about 1 second maximum for Nasdaq, depending on the stock's liquidity (you didn't say anything about that last point, nor whether it's a listed or Nasdaq stock).
Anyway, if you trade volatile, liquid stocks you really have no choice but to go EDAT. Otherwise 10 seconds can...
1) feel like a lifetime
2) cost you a fair chunk of change