I have several accounts, and there's a definite tradeoff for high interest vs features.
If you plan to sideline cash a lot, Bank of America's trading account is currently paying 4.53 in the sweeps, and it's only $5 a trade (BOTH market and limit). They're a typical bank when it comes to daytrading (not to mention that they don't instantly update, and while you can sort of daytrade... something new for them... your cash is immediately available now, it still looks all messed up for 5 days in your account balance due to the settlement date thing- I do it all the time anyway).
You can get 30 FREE trades, no commissions, a month if you have only $25K in their bank (can do CD's, not just banking). It's a great deal, and the bank account lets you see your investment accounts all at once. Also, I trust their accounting a hella lot more than any small brokers, who don't track your cash nearly as obviously. Etrade did and still does strange things in their accounting (like I got a dividend payment once for $290 for only 300 shares of a $10 stock, which vanished the next day from my account, and then foreign taxes were taken out on that $290, then returned, but it only turned out to be $17 in dividends, and then the $17 was removed.... and they couldn't explain it by phone ... things like that).
If you like options and daytrade, interest is really low or nonexistent on the cheaper comission brokers. But if you want to do options, Think or Swim is fantastic for their free options software, free education, execution time, etc., even tho they're more expensive than IB for commissions.
If you do less than 30 trades a month and if you sideline a lot of cash, the interest definitely matters, so you may want to look into Bank of America for commission free trades, not too bad research (you get all the S&P/Argus/Sabient reports free), and the best accounting. If you want to do options, forget Bank of America, ThinkorSwim is awsome. Then you have to store your $$ in an ETF or a bond fund.