You are correct. The tax treatment is the same whether you take the dividend in cash or re-invest it in the DRP.
One negative that some analysts give against DRPs is that people tend to enrol and forget, accumulating more shares as the years go by. Some say that is bad decision making and that you should always actively assess whether to invest more in the company every time you get a dividend. Perhaps the best decision may be to hold off purchasing more (if the shares have become overpriced) or instead invest the dividend in some other company's shares.
Remember that CBA pays dividends twice per year, so you should use the interim and final dividend to make a comparison.
One can't say that dividends pay a higher return than bank deposits. Some do, some don't. Banks usually do and some companies like Telstra pay over 9%. Other companies' dividends may be a lot lower.
What you should watch out for is the combination of capital gains and dividends. There is no opportunity for CG with bank deposits (and little possibility of loss too). The high dividends of some companies', like Telstra in particular, have not made up for their pathetic SP performance (Telstra T3 was at $7.50 I think, but they trade now around $3). Some companies have not only paid good dividends, but also have rewarded investors with a constantly increasing SP.