This is a discussion that will never die. It baffles me, however, that so many people accept the premises of the anti-english crowd, without any critical analysis. Many of them are just plain wrong, especially when applied to an advanced player. This is my case for the (frequent) use of english.
For the sake of my analysis we will call the sum of the cue balls speed and spin its "energy".
1. All pockets have a range of speed in which it will more easily accept a ball. If the OBJECT ball approaches the pocket at speed faster than this range or in rare cases, slower, the pocket is more likely to reject the ball.
2. Most players have a comfort zone for the speed of their stroke. At high or extremely slow speeds, many players tend to be less accurate.
3. Whenever the cueball and object ball collide at very slow speeds, there is an added risk of cling or bad contact.
4. Whenever an object ball is close to, or frozen to a rail, using sidespin will give the cueball many more possible directions in which to move.
Knowing these four things we can conclude the following:
A: Using sidespin will make it possible to keep the object ball speed within the pockets acceptance range, even for shots where the cueball has to move a long way, because the sidespin will add energy to the cue ball, which will translate to movement when hitting rails, while keeping the object ball speed the same (more or less).
B: Likewise, using sidespin will allow the cueball to be moving very slowly, while still cutting the ball cleanly, because the relative speeds of the colliding surfaces will be higher than a plain rolling or sliding cue ball.
C: If you have a shot that calls for either an extremely slow rolling cueball hit with an awkward slow stroke, or a very hard shot (with centerball), english will give you many opitions using a comfortable medium stroke, by the use of either "kill english" or "running english". Thus you get to keep your stroke in its more comfortable range.
D: English will make position routes from rail shots possible, that just arent possible with center ball.
5. Many "anti-english" advocates state flatly that shooting most shots without english makes you more accurate. I reject this argument. It is true that certain elevated shots, from the rail or over a ball, and long shots hit with an unfamiliar "off" speed can be tricky, but most medium or short range shots can be greatly simplified by adding either a touch of inside or a touch of outside english. It is true that at the extremes of english it can sometimes be a bit tougher, but in those cases you will most likely have weighed that against other factors. For most common shots, adding a controlled amount of english for an advanced player will either be positive for the pocketing ability or more or less neutral in its effects, once the other factors have been accounted for.
6. English does not make you lose control of the cueball speed. I don't know what nincompoop came up with this "gem" but I'm pretty sure he didn't play at a high level. Mike Sigel shot most of his shots with a touch of outside. How good was his cueball control? I can only guess that the person(s) responsible for this drivel shoots all their english shots with one "amount" of tip offset and only at a small, select range of speeds. Otherwise it makes no sense at all. If anything, english greatly increases cueball control by making ideal angles possible, which will greatly increase the range of speeds within which the shot will be a success. It will also help with holding the ball or making it run respectively, which also increases error margins.
7. Snooker players...blah, blah. Snooker is a game I know quite a bit about. It is played on a much larger surface, which means most shots will have plenty of time to alter the tangent angle of the cueball before it hits a rail. Snooker rails have square noses which means that they will not grab the cueball as much. As a result you will get much less of a change of angle from your english. The snooker cloth is usually slower and the balls are lighter which makes them hold on to spin for a shorter time. In addition the cloth has a nap, which causes all kinds of weird effects, which would surprise most naive pool players. To defeat the nap you need to shoot most shots a bit firmer than on a Simonis surface, or somehow account for the effects. The sum of this is that english is A BIT less useful than on a pool table. That still doesn't mean that snooker players don't use english A LOT more than they are given credit for.
END RANT
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