Rick:
Although snooker balls are about 5% smaller than pool balls, it's not their size itself (whether smaller or not, doesn't matter) that has any bearing. Rather, it's their size
in relation to the size of the pockets on the table that has the bearing.
Look at a
Russian Pyramid table and its set of balls (probably the tightest ball/pocket clearance of any cue sport). Russian Pyramid balls are the largest in the cueing sports, yet the extremely tight pocket clearance is what sets the potting difficulty of this sport apart from pool (other than the rules of the game, of course, where caroming the cue ball into a pocket is considered scoring).
Comparison of 68 mm (211⁄16 in) Russian and 57 mm (21⁄4 in) American-style pool balls.
It is the fact that in snooker, there is very little pocket slop in comparison to American pool equipment. In addition, in snooker, the pocket facings are rounded, and NOT chiseled, which will reject a poorly-hit ball. You can get away with hitting the chiseled face of an American pool table pocket, and as long as you don't slam it, the pocket will accept the shot. Try that on a snooker table -- hit the rounded face of the pocket -- and the pocket spits the ball out. (You can get away with lightly -- and I mean very lightly -- grazing the innermost edge of the rounding, but if the ball hits any part of the rounding with a good percentage of the ball itself, "it ain't going.")
Thus, in snooker, you aim at the center of the pocket. Not any pocket chiseling, not the adjacent rail to "help it in" (as is done on a pool table when sending balls down the rail); just the center of the pocket.
Also, you don't have the plethora of "alternative aiming techniques" like you have in pool. For instance, in CJ Wiley's "touch of inside" aiming technique (discussed in the Aiming Conversation subforum), he advocates pushing all the pocket slop to one side of the pocket, by aiming slightly "full" and with slight inside spin and with an accelerating stroke. He's leveraging the deflection characteristics of hitting a cue ball slightly off-axis (slight inside "side") to "deflect" the cue ball to cut the object more. This technique absolutely requires the pocket slop inherent on an American pool table, because the aim ISN'T at the center of the pocket. This technique would NEVER work on a snooker table. But the technique IS leveraging (exploiting?) the characteristics of American pool equipment, and it can be used successfully in that environment only.
Also, there's no such thing as CTE in use in snooker -- at least in the accomplished player ranks (i.e. not a pool player "trying his hand" at snooker). You either aim at the center of the pocket, or you don't. The rest would be considered "leaving it to chance that you get the pivot right to put you on the exact line to pocket that ball center pocket."
Getting to the meat of answering your question, the heart of a snooker player's accuracy is his/her FUNDAMENTALS. A snooker player's fundamentals "locks in" the player's body to the shot line, it "locks in" the players stroke arm to that foundation, and doesn't allow the wavering or loosey-goosiness that you see in pool player stances. This video demonstrates:
http://youtube.com/watch?v=gSK4w_9S_x0
Notice how solid the snooker stance is, and how, well, "wet noodly" the pool stance is by comparison.
Also, teaching and coaching in snooker is by and far more regimented compared to pool. There's even a published syllabus that goes w-a-y back, that most (if not all) snooker instructors and coaches teach from. Compare that to pool, which traditionally has been a "learn as you go" approach. The former enforces that all aspects of good fundamentals are covered, while the latter encourages laziness -- where the player picks and chooses what he/she wants to learn, according to the "fad of the day" or what he/she sees as a "magic pill."
Thus, in pool, basic fundamentals such as proper head/eye alignment to the shot line (including the discovery of what is one's "vision center" and the bearing a dominant eye has upon it) is never learned, or learned through "fad of the day" teaching techniques as you see being aggressively marketed on the pool forums. Those "marketing for a buck" techniques are doing a service though, in that they attempt to plug a hole or two in the swiss cheese approach to learning pool.
Summary: snooker's greater accuracy is a "fallout" -- a result, if you will -- of proper teaching techniques and proper syllabus/learning on the part of the student. Pool's lack of it (lack of same level of accuracy, that is) is a result of the mindset of "get what you need to make it good enough for government work," as well as a result of accepting what the equipment allows vs. exploiting the equipment intentionally.
Hope that helps?
-Sean