ping isn't half the story. Yourt order needs ot come across the water, and then internally STOP at the broker for checks vs. easy to borrow, margin,and maybe disaster recovery, and then be sent to the ECN or exchange. then, the latency per exchange varies wildly by their matching technology. Also, what about throughput? If it's high traffic time, you've got the width of the pipe to deal with as well, not just a ping time. You really need to look at the entire round trip, not just a ping, to make sure you've made a good choice. Round trip is a function of your over the water pipe, internal broker latency, round trip times form broker to ECN, ECN technology, and back. Ask all those questions...!!!
UH...unless i am wrong by a factor of 10, a "ms = millisecond" is one thousandth of a second. If your reaction time (let's say the time it takes to recognize an opportunity to trade + the time it takes to hit the key) is 15 to 45 seconds (15000ms to 45000ms)....maybe you should do something a little longer term. Or stop trading.