Suisei definitely shows her experience, she has that extra emotional quality to her singing. Something IRyS has lacked in her covers so far, though I expect she will improve now she's with Hololive.
Marine's original "Unison" has really tickled the special part of my brain and I've been listening to it non-stop all day, I miss back when I used to use "itunes" only for the fact it tracked how many times I'd played a song, because I wonder if "Unison" will beat my longest record of listening to the same song 268 times in a row, before I finally went back to other stuff.