If the rising rate cycle is over for the next several years, than locking into a high yield CD will likely return more than keeping your money in a savings account. Once the Fed starts to cut rates, the savings account rates will also fall. On the other hand, inflation could lead to higher rates. You may want to try to make predictions based on history. Here are some references for rate history: Intended federal funds rate since 1990 and T-Bill History since 1928. Please leave a link if you find any other good references.
Even if rates do rise over the next few years, a CD could still be the better option. For example, let's say one person purchases a 6.25% APY 3-year Penfed CD and another person puts money into E-LOAN's 5.38% APY savings account. And let's assume rates do rise over the next 3 years. If the E-LOAN savings account rate rises to 7.12% at the end of the third year, the average return for the 3 years would be about 6.25% (average of 5.38% and 7.12%). So in this case, both would end up being about equivalent. So a CD could be a better option even with rising rates when rates don't rise too much.
One important concern would be a case in which rates go way up like they did in the early 80's. In that case, the savings account would come out ahead. But a CD may not be too bad especially if the early withdrawal penalty isn't too severe. The Penfed CDs with terms of 3, 4 and 5 years have a maximum early withdrawal penalty of 180 days of interest. The 7-year CD has 365 days of interest penalty. As an example, if rates jump after 2 years, you may find it worthwhile to break the CD. The loss of interest would turn the 6.25% APY return for those two years into a return of about 4.70% APY.
These are just some considerations that may be helpful in your decision. For more information on Penfed and its 6.25% CDs, please refer to this post. For a list of high yield CDs and savings accounts, please refer to my weekly summary.