I have owned 2 Supras, a 17 SA400 with the Acme 2775 prop and now a 18 SL550 with the Acme 2247 prop My buddy has a 19 SL450.

My SA had 650 pounds of lead and with 4 adults and 2-3 kids it always struggled when the ballast was full to get on plane. I would have to move more people to the bow, drain ballast and switch to the advanced wakeboard profile to engage auto-launch and still it would take forever to plane out.

The 550 is obviously a different story, but my buddies 2019 SL450 is night and day different than my 400 was.

If you can demo both the 400 and 450 I would load them all the way up and see what you think. Personally I would not buy the 400 motor in a SA or SL, but I would be happy with the 450...it's a big noticeable difference over the 400.