No sign bit
Negation is a per-digit flip, so it is carry-free and costs one cycle.
There is no two's complement, no INT_MIN asymmetry, and no
signed/unsigned split — one ADD, one MUL, one
CMP instead of two of each.
Truncation is rounding
Chop a balanced-ternary number short and you land on the nearest
representable value, always. The discarded tail can never exceed half a
unit in the last place. No rounding modes, no guard digits, no
round-half-to-even.
Comparison returns one value
Asking whether a < b has three possible answers, and a
trit has three states. One instruction returns less, equal, or greater —
where binary machines need condition-code pairs to encode three outcomes
in two-valued logic.
“Unknown” is a value
The third state carries missing or indeterminate data natively, the way
SQL's NULL does — but in hardware. No sentinel values, no
parallel mask arrays doubling your memory.