With more than 100 online brokerage firms to choose from, choosing the right one can be intimidating. Some of the broker rating guides published by Barron’s, Kiplinger’s and others are helpful, but investing is a personal activity. A broker that appeals to a wealthy investor might not be appropriate for those with only a few hundred dollars to invest.

The good news for investors is that intense competition in the industry has closed the gap among firms on price, quality of service, products and speed of execution. The most active traders in particular will pay about the same commission fees at Fidelity, E-Trade or Ameritrade.

“Once you get to the very high levels of trading, the difference between firms isn’t that much,” said Timothy Carpenter, senior analyst at Watchfire GomezPro. “Even the most expensive firms are charging at most $10 per trade.”

A good starting point to winnow down the firms is to first ask, “How much do I have to invest?” Some firms, such as Scottrade, require only a $500 minimum, but others like Fidelity require $2,500.

Second, decide how many trades a month or quarter you plan to make. Most brokers link the commission fee to the trading frequency. While the most active traders will pay about the same no matter the firm, the fees vary widely for less active traders.

Finally, decide how much help, advice and research you need. Most industry experts agree Fidelity has one of the best Web sites and offers some of the best financial advice. However, it’s among the pricier brokers for the nonactive trader. Additionally, almost all the firms now offer investing advice, tips and research reports.

“The truth of the matter is that of the top 20 firms, almost any of them would be the best one depending on the needs of a particular customer,” Carpenter said.