This one is an interesting case of how regional and technically revision differences for a game can change how it's played.
Review:
Another helpful link for regional differences, as well as a good video about how some of the game code was developed and how it works can be found here:
https://tcrf.net/Dragon%27s_Lair_(NES)
The run for the JP version that I'm doing my comparisons will be with the recent submission:
#7805: ktwo, MESHUGGAH & Kirkq's NES Dragon's Lair in 03:50.70
To properly compare the gameplay portions of the game, I had to have videos side by side but adjust one video's speed to match the gameplay FPS as listed from the SDA Knowledge base. More specifically, I just ran the JP run at 60% speed to match the US frame rate. That way it's more possible to make stage by stage comparisons.
Stage 0
The US run is behind by frames. The US run does a jump over the broken-when walked-on part of the drawbridge while the JP run breaks that part early.
Stage 1
The second snake despawns in the JP run before Dirk can walk into it which leads to that version being roughly 2 seconds faster. Not sure if the US version can do the same or not. Also worth noting that this marks the first point that some factors, in this case the gates, have different timings between the versions which accounts for some slight timing differences and approaches.
Stage 2
Again the timing differences for the pillars and the boss patterns are different. Due to movement differences possibly due to control reasons, the JP run gets through the stage area faster. However due to the JP version moving the screen position and the player when the boss spawns, as well as different boss patterns, the US version is faster here and the runs are close by frames. It's close enough that it's hard for me to tell which is the faster one overall in this case.
Stage 3
Another case of timing differences with certain parts of the level. The big one is a moving platform that has a different timing in the US run that both requires another jump to make a gap rather than walking across as well as the unavoidable extra gold that has to be collected. The extra gold results in a slightly longer results screen duration. While overall slower for this stage, the US run has a much faster boss fight due to a different floor layout. Without pits, Dirk can just waltz up to the boss and jump up for fast strikes for the quicker kill. The JP run has to do some extra avoidance of projectiles and pits which makes for a slower fight.
Stage 4
The JP run through the stage is slightly faster for two reasons. One is just better movement, possibly due to control reasons. The other is that the JP run does not have to worry about skipping the dagger pickup at the end. Since the final boss can be bypassed in the JP version, weapon choice is not a worry. Since this isn't an option for the US run, an extra jump has to be performed to skip the detrimental weapon pickup. The US run then proceeds to fight Singe which seems clean in execution.
Overall, when put side by side and with adjusted speed to compare the two the JP run is comparatively faster but not by that much. A lot of the differences are likely just by virtue of player control differences and level pattern differences. The US run having unique strats not seen in the JP run also makes it a unique experience outside of the gameplay speed.