I'd have to go with Ronnie O'Sullivan's stroke/cue action. I categorize his stroke as somewhere in between a pool stroke and a snooker stroke. His stroke is not overly-mechanical and contrived unlike most snooker players'. It is a flowing action--his follow through and overall delivery is reminiscent to that of a pool player's.
The integration of elbow drop, couple with his exceptional gift for timing allows him to accelerate and cue through the ball better than any cueists--pool or snooker. This enables him to perform a lot of pool-esque shots on a snooker table. The combination of deadly accuracy and effortless power makes his stroke compatible for any cue sports table that has six pockets in it.
Efren Reyes' stroke is a close second. On a pool table, his stroke is unarguably as good as you can get. But the wavy nature of his stroke, due to the involvement of shoulder movement and unorthodox grip, invites more inconsistency--and such inconsistencies are magnified on tighter pool tables, let alone snooker tables. You will never see a top snooker player hold his cue with only his thumb and forefinger and release the cue at the moment of strike. While this enables Efren to cue through the ball just as well as Ronnie, it will take years for someone to replicate his unique delivery. There are simply too many moving parts involved. He was able to pull it off because he has the best rhythm--his feathering is akin to someone playing the violin, and this very fluid and consistent pre-shot routine gives him full confidence as he strikes the cue ball.
The fact that Efren remained in the top echelons of pool for as long as he did with that seemingly cartoonish stroke is testament to his otherwordly talent. I'd go so far as to say he's more naturally gifted than Ronnie!
If you look closely though, Ronnie's and Efren's final delivery of the cue are actually quite similar. Ronnie's final backswing in particular looks like a slowed-down version of Efren's.
Why not Stephen Hendry's? While his cue action is definitely the gold standard with regards to snooker fundamentals, his cue action is too deliberate and may not necessarily be translatable on a pool table. The main reason for his success wasn't his cue action, but his unbelievable temperament.
A perfect player in my view: someone who possesses Ronnie's stroke/cue action, Hendry's temperament and determination, and Efren's creativity, personality and longevity.