Sound holes or not? For and against! My 2 string bass has no holes, and sounds good to me, but.
I say season to taste... some boxes look good with sound holes, most I like as they are. But...
On this solid rock maple bass, I routed out the back of 2.5" square stock body to reduce weight and improve balance....then cover cavity with a plate of resonant sinker cypress w/ sound holes. Pickup on this 34" scale 3 string (ADG) electric are dual under-bridge piezos direct to output jack.
I vote sound holes + pickup.