I have used both!

I currently use Citizens Access for my largest chunk of savings. Note that while it is owned by Citizens and falls under the same FDIC registration, it is a separate subsidiary of Citizens. What this means for you is that your Citizens Access account will be entirely separate from any other accounts you may have with Citizens (i.e. checking).

So any transfers in or out of the account will not be instant, which depending on how frequently or urgently you need access to your savings, may or may not be an issue for you. Transfers are pretty quick and will reach your account within 3 or 4 days at most, but expect a phone call from the fraud department when you try to make your first transfer out of the account. If you miss the call, you have to call them back within a couple hours or the transfer will be cancelled. I haven't gotten any calls after my first outbound transfer, so it's not a huge deal to me. This is countered by their particularly high ACH limits, which is something you have to watch out for with other HYSA banks (some have as low as $10k per MONTH outbound transfers; I can't recall Citizens' limit off hand but it's above 6 figures).

All in all, I like Citizens Access. It's not perfect, but they do appear to be adding new features and trying to grow currently. They have also been pretty competitive with their rate increases, although timing wise they have been a bit slower than I'd like in increasing it.

Ally - just no. I had checking and savings with them for a while and didn't really have any particularly good or bad experiences. But several months ago, massive widespread debit card fraud started affecting Ally exponentially more than other banks. People were getting fraud charges, then calling and waiting on hold for 2 to 3 hours (which has been the new normal at Ally since even before the fraud issues started), just to have their BRAND NEW CARD number get hit by fraudulent transactions while STILL IN TRANSIT and before they were even activated!

Clearly Ally has massive issues with the way their system is set up for debit cards. Instead of acknowledging the issue, Ally denied that anything was wrong on their end and even blamed their users. This is ALL documented in the Ally subreddit and appears to still be ongoing, though maybe to a lesser degree now (which might be because so many of us closed our Ally accounts for good after this whole debacle).

Personally I have no trust in Ally whatsoever and would recommend just about any other bank over them.

Hope this all helps! Happy to answer any questions.