It really depends what you're drilling. Assuming this is for porcelain then there is very little to beat the electroplated holesaws and a sponge on a cost per hole basis as they are disposable.
Some of the more expensive water fed systems (like Marcrsits for example) are ideal if you've got hundreds of holes to drill regularly, but can be a bit overkill for the average tiler.
On the occasions when you need to drill dry then there's always a compromise between cost of bit and number of holes it will produce. As a rule of thumb drilling dry is always going to shorten the life of any bit.
Vacuum Brazed Diamond bits designed for drilling marble also work in Porcelain to a reasonable degree. The smaller ones have wax filled centres to disperse heat.