This (big vs. small) was transformed from rumor/gossip/opinion over 100 years ago. Dr. Lanchester's formula to predict outcome of a 4-stroke engine is still accurate, where:
B = bore diameter
S = stroke length
N = number of cylinders
C = a constant representing quality of materials and fuel energy value.

HP = B^1.65 × S^.5 × N × C

As you can see, displacement is far less valuable than large bore and more cylinders. Note that there is no factor for valve mechanism or number of valves. A significant flaw: no correction for mandatory parasitic loads which are disproportionately high for small engines: water pump, oil pump, cam drive, ignition.