I've found that the yummy little cherry toms such as Gardener's Delight and Sungold are prone to some splitting whatever care you take over watering. This probably explains why these varieties are rarely sold in shops. The cherry toms that are usually sold are thicker-skinned and usually flavourless little nasties. One exception is a variety called Piccolo which is sold at premium price in some UK supermarkets. They are quite thick-skinned, rarely split and are pretty tasty, especially the Italian ones. Maybe I'll try growing 'em next year, but this year it's Sungold in me greenhouse. There are always enough unsplit ones to satisfy, and the split ones are very nice done in the oven or grilled for five minutes sprinkled with olive oil, basil, salt and pepper. Garlic too if you're feeling sociable.