That's exactly the purpose of an RCA. When it comes to tax planning for wealthy taxpayers, generally speaking, you have three options (the "3 D's" of tax planning):
- Deduct - claim expenses to reduce the amount of taxable income
- Defer - shift the income into a future period
- Divide - shift the income to someone (ie family member) in a lower tax bracket
The RCA is a powerful tool for the 2nd D - deferral. Deferring income tax into the future is (generally speaking) a good idea. It's especially useful for professional athletes, since the majority of them will earn a very high income for a relatively short time frame. The benefits are 1) when the player's career is over, they'll likely be paying tax at a much lower rate (so you have a direct reduction in taxes payable) and 2) shifting the income to the future means the NPV of the payments will be substantially lower (ie better to have to pay $1M in 15 years rather than today).
I agree that, conceptually, there are similarities between an RCA and an RRSP. The biggest advantage is an RCA allows for substantially higher deductions. There's absolutely no comparison as to which is more beneficial for athletes (or executives or small business owners).
An RCA isn't the right solution for every athlete, and there are certain drawbacks that need to be considered. But, if structured properly, the advantages can be considerable. In fact, in the NBA, RCA's are banned because the league believes they give the Raptors an unfair advantage (but this advantage is available for all seven Canadian NHL franchises).