Gee, Archie, you're disagreeable today!
The reason 2400 isn't considered to be suitable for .38 Spl. anymore is because of the huge amount of powder that's expelled from it unburned.
There are other powders that burn a lot more efficiently that give virtually the same velocity curve, more efficiently, with less stress on the gun and shooter.
But you do touch on an important point.
Of the 3 choices, none is really truly suitable, but all will work.
Bullseye and Unique are pretty fast, and 2400 is way too slow.
Of the 3 choices, though, I'd go Unique. It's faster than 2400 and slower than Bullseye.