SHORT ANSWER
Stack'Em and Fist of Destruction both use expanding symbols but implement the mechanic differently. Stack'Em's expansion is more frequent and more spread across the base game. Fist of Destruction's expansion is tied to a specific symbol type with multiplier potential, concentrating the mechanic's value into fewer but larger events.

How the expanding mechanics differ

Stack'Em uses a stacking expansion mechanic where symbols can stack and expand across adjacent positions on the grid. The expansion is frequent — contributing to many small-to-medium base game wins — and is less tied to a progressive bonus escalation system. It produces a more consistently engaged base game at the cost of fewer big spikes.

Fist of Destruction's Fist Wild expansion is more selective: only the specific Fist symbol expands, it expands upward only, and its value is tied to multipliers collected from Fighter punches. The expansion is less frequent in the base game but carries more concentrated value when it occurs — particularly in bonus states where pre-loaded Fists can stack multipliers multiplicatively.

METRICFIST OF DESTRUCTIONSTACK'EM
Best RTP96.30%~96.00%
Hit Frequency34%~38%
VolatilityMed-High 4/5Medium 3/5
Max Win10,000x5,000x
Expansion typeUpward Fist Wild + multipliersSymbol stacking expansion
Expansion frequencyLow-moderate (Wild appearance)Higher (frequent stacking)

Base game experience

Stack'Em's higher hit frequency (approximately 38%) combined with more frequent expanding events means the base game is more active than Fist of Destruction's. If you prefer a slot where interesting visual events happen regularly — symbol stacking, small cascade wins, active reels — Stack'Em delivers this more consistently.

Fist of Destruction's base game is quieter: frequent small standard wins from the 34% hit rate, occasional Fist Wild events that create spikes, and the grind toward bonus trigger. The expanding mechanic feels more significant when it does appear precisely because it is less frequent.

Which is more efficient for the expanding mechanic specifically

If the goal is extracting maximum value from the expanding symbol mechanic per unit of bankroll, Fist of Destruction has the edge. The multiplier component of Fist Wild expansions can convert a single expansion event into a 50x to 200x spin in the right conditions. Stack'Em's expansions produce smaller, more predictable returns per event.

Fist of Destruction's 10,000x ceiling versus Stack'Em's 5,000x reflects this design difference — the concentrated, multiplier-rich expansion mechanic supports higher theoretical maximums than the more distributed stacking approach.

For casual players: Stack'Em's lower volatility (3/5 vs 4/5), higher hit rate (38%), and more active base game make it the more immediately engaging slot. For players who specifically want to explore the high-value expanding wild mechanic in its most developed form, Fist of Destruction is the better vehicle.

BOTTOM LINE
Stack'Em and Fist of Destruction both use expanding symbols but in fundamentally different ways. Stack'Em produces more frequent small expansion events with lower peak value. Fist of Destruction produces less frequent but higher-value expansion events with multiplier potential. Stack'Em is better for casual session entertainment; Fist of Destruction is better for chasing large single-spin outcomes through the expanding wild mechanic.