For all practical purposes, NCUA insurance coverage (credit unions) is equivalent to FDIC insurance coverage (banks). That said, you may find a credit union with so-called "private" insurance, offered by ASI. Many folks (including yours truly) feel, well, less than comfortable with anything less than "full faith and credit" NCUA/FDIC coverage.
Moving right along, I am also less than comfortable with banks or credit unions with poor ratings (you can find more info on this over at http://www.depositaccounts.com
, where Ken Tumin often discusses such arcane details such as "Texas ratios"). Even if a CD is federally-guaranteed, should the bank or credit union go belly-up, your CD is subject to re-pricing by the acquiring institution (i.e., bye-bye to that good rate and term, most often). If no acquirer can be found, you get a check for principal and accrued interest, and have to find a place to plop the funds (post-haste, if an IRA CD).
If you have IRA CDs and are over 59 1/2 (as I am), you should look at PenFed. They allow partial withdrawals from IRA CDs without penalty for early withdrawal. Northwest FCU and StateFarmBank do as well, but PenFed's rates tend to be better. Some financial institutions don't allow partial withdrawals, period. I think Ally is in that category.
Of less concern (to me, at least) is customer service. I usually deal with the financial institution only twice, when buying and redeeming. But little things count. For example, if you are contemplating a custodian-to-custodian IRA CD transfer, will the new custodian (the bank or CU to which you are transferring the funds) lock the rate and term upon application? If not, and the rate and/or term evaporate before your funds arrive, you could be in for a rude shock.* And sometimes you just have a question about your account, so you might want to avoid a financial institution with a toll-free number that routes you to a 20-minute wait (I could name names; PM me).
*For example, you want that 5-year CD at 2% for your ladder. You fill out all the forms, send them to the prospective custodian, who sends them to the current custodian, who cranks out the money upon maturity and snail-mails the check to the new custodian. By the time the check hits the "CD desk" at the new custodian, "poof", like magic, that 5-year CD is now at 1.5%. Now what? To avoid this, I always get written confirmation of a rate-lock and (belts and suspenders) send a very, very clear cover letter with any transfer request that, should the rate and term I want not be locked, the transfer request is withdrawn.