Each type will stimulate an improvement in muscular strength and endurance. However, when it comes to the degree of improvement they are different. Isokinetic training is considered by most to be the best way to train a muscle. Isotonic training is probably the next best thing to isokinetic training. This is the result of the benefits of leverage at certain points of the lift, which makes the lift easier.
Isometric training is considered the least effective.
This is due to the fact that strength gains are specific to the angle of muscle contraction. This means that if a joint is in a 90 degree angle during the isometric contraction, the muscle is strengthened primarily at that angle. Angles greater or less than 90o, strength gains are not as great. It goes back to working the joint through its full range of motion. Isometric training is most beneficial in sports where static contractions are performed regularly.