In my opinion, tight tables will help your game BUT:-
1) Confidence far outweights any need for practise on tight tables. If you have no confidence in your game a tight table won't increase confidence that much.
2) Even if you gain confidence there is a mental hangover. You go from 4" pockets to 5" or maybe even more and for 99% of people they will think the game is easier because they play on tighter tables. These same peoples speed will not improve an awful lot more because the problem isnt pocketing the ball, its the resultant position following the shot!
With this in mind it is my belief that tight tables help your fundamentals but anything less than 4" is not a good game table. I despise big pockets where a lot of shots can miss by a long way and still go in. 4" is perfect balance.
3) The way I aim takes out of the equation any risk of losing discipline, all I know is I have more options of WHERE to pocket the cueball. On a tight table I can split it into 3 parts maybe on bigger pockets I can split it into 5...
4) I have transferrable experience from darts to pool of playing on tight equipment, as in darts there are boards made with 1/2 sized trebles, doubles and bull. Again people (and me included) had this belief that hitting the smaller trebles would help hitting bigger ones. All it does is make you FOCUS more. For all intent and purpose you could stick a piece of string to a dartboard and try to break it several times, but this will not help you much in a match situation. Sometimes trying to be too precise can be the end of you, technically speaking you have to be fluid and having to focus too hard will ruin you.
In short - tight tables great for fundamentals, control and discipline...but all in moderation. Its important to treat the game with respect at all times, and if you are used to tight tables it can then make you lazy on bigger tables. Treat all pockets the same...dont be a maverick just because a pocket is .5" bigger
Sorry for the epic post and sorry if I offend anyone by having a difference in opinion...
Shoot well,
Baz