I think Samson is really handsome!! It’s a lovely choice.
For me, it sort of depends on the vibe of ypur other childrens’ names. There are names that are uncommon but still feel familiar (e.g. Oriana, which isn’t in the US Top 1000 but feels familiar because Ariana has been popular, or Mina, which is outside the Top 600 but has a simple & lowkey sound) and there are names that are uncommon and really feel like it too (think Ferelith and Alcyone). If your children’s names feel more like the former, I think Samson works well even if he does become Sam! Even if he does go by Sam casually he still has a unique full name to fall back on.
That said, at the end of the day it’s up to you if it would bother you if he was often nicknamed Sam or if he decided to go by that when he’s older.