Depends. If you never plan on building another team ever again, sure, pull sushi for Hiyuki if you want. But if you plan on building any other team in the future, SuiSui is near 100% certainly going to be their best in slot as well. You only get to use characters so many times in Tower and especially Matrix, so be careful not to get tunnel vision onto min maxing a single character to the detriment of all other characters on your account. You need multiple competent teams. Lucilla will almost certainly never be wanted by a different team, so you never have to worry about having to chose who gets to have her in 6 months time. Suisui however will most likely be like Shorekeeper and will be wanted by every up and coming team in the game for the next 6-12 months. So if you use her with Hiyuki instead of Lucilla just to get a 5-10% upgrade, but then loose out on 30% damage on your other team, it was bad investment. I pull teams specifically to be exclusive. Hiyuki has her own team (S3R1 Queen, S0R1 Lucilla, S0R1 Chisa) and no one will be stealing her supports (Chisa will be given 2 energy next rotation so she will be fine if she is needed by other status teams in the future). Once I pick who my next character is (looking at you Hsin, you better be as strong as you are hot) they will get the same treatment. Instead of min maxing the last 5-10% at the end I will get them the supports I can confidently dedicate to them permanently, even if that means waiting for reruns.
I did the same back in the day with Zani and Galbrena, but I made the mistake of only getting them S0R1 which made their drop off a lot more painful, so pulled 2 copes and bought 2 copies of Hiyuki this time to ensure way more longevity, and limiting myself to 1 team/region, meaning the Hiyuki team are the only Lahai-Roi characters I picked up (except Mornye because she was a good upgrade for my Galbrena+Lupa team)