Major discount brokerages have slashed the commissions that they charge investors to trade US stocks and exchange-traded funds (ETFs) online. But before you decide on where you will do your trading, there’s more you should consider to get the true cost.

The price war among brokerages includes a drop to $4.95 per trade by Fidelity Investments (formerly at $7.95) and Charles Schwab (formerly $8.95)…and to $6.95 at TD Ameritrade and E-Trade (both formerly at $9.99).

Additional factors to consider…

Do you tend to invest often in ETFs rather than individual stocks? If so, then also consider Vanguard. Though it typically charges $7 to trade stocks and ETFs (or $2 if your account assets total $500,000 or more), Vanguard charges nothing for trading its 70 in-house ETFs such as the Vanguard S&P 500 ETF (VOO). Schwab offers more than 200 ETFs commission-free (including ETFs from SPDR, PowerShares, WisdomTree and Guggenheim)…E-Trade, more than 130 (including WisdomTree and Guggenheim ETFs)…TD Ameritrade, more than 100 (including iShares, Vanguard and SPDR ETFs)…and Fidelity, 91 (including 70 iShares ETFs).

How much assistance do you need? Prices vary depending on whether you trade online or do broker-assisted trades on the phone. The Ameritrade and Schwab websites are particularly easy to navigate, so you are less likely to need broker assistance. The cost of a broker-assisted stock or ETF trade by phone is $25 at Vanguard (or $2 if your assets total $500,000 or more)…$29.95 at Schwab…$31.95 at E-Trade…$32.95 at Fidelity…and $44.99 at TD Ameritrade.

What to do: Don’t be lured only by low online stock-trading fees. To choose a brokerage, consider the entire mix of trading you are likely to do.