Apparently some people pronounce, or have pronounced, Ian to rhyme with Brian, so anything is possible.I like both, but Rhys has no personal associations for me so I would definitely use Ian, to honour two dear friends and an ex-BIL.
I definitely prefer the name Ian due to it’s sound. It’s also not very common where I am, either. So, I do like it! Rhys is also a very nice name, but I kind of prefer the Reece and Reese spellings.