Steve Olesin replies: For a short answer, my personal choice is fewer teeth on a really high quality blade that is kept sharp.
For a better answer, maybe we can recast the question to read – “What are the tradeoffs in selecting blades for the table saw.”
First, the table saw throat plate must be replaced with a zero clearance plate to allow for greater surface support of the wood being cut. This reduces underside chipping. Next, the fence must to aligned parallel to the to blade. Finally to cut cleanly, a blade must have minimal runout (wobble) plus all the teeth must be sharp and of the correct geometry.
Given an identical feed rate, the following is true. A greater number of teeth will take smaller cuts per tooth which could improve the finished surface. A greater number of teeth will reduce the maximum feed rate by reducing the chip carrying capacity of the gullets. Plus, increased tooth count increases friction and heat generation. Thick wood also increases the temperature of the cut surfaces. The density of the woods being cut effects the amount of distortion around the cut, which translates into the fuzziness of the cut surface. Softer woods benefit from a higher tooth count because each tooth takes a smaller bite. This distorts the wood less thus leaving a smoother cut surface. Cutting cherry with a high tooth count blade may result in enough heat build-up to discolor the wood.
Rip cutting tooth profiles are square to the blade to create the effect of many chisels taking small chips out of the wood. Rip blades cut cleanest when cutting along the grain.
A cross cut tooth has alternate pointed edges to allow it to slice across the wood grain versus chopping it. Cross cut blades are the preferred blade on a chop saw or a production table saw that is set up for only cross cutting. It is generally a mistake to install one as the only blade on a tablesaw that is used for a variety of work.
A combination blade is just that – a combination of both profiles. Not great for either job but when sharp, we don’t tend to notice. Here the choice of tooth count comes back to the types of wood being worked. Thick hardwoods do better with a lower tooth count. Thin hardwoods and most softwoods or composite materials cut cleaner with a higher tooth count. This is because the chips being taken out of the wood structure are smaller.
If we vary the feed rate, we can get the best of all worlds by using a low tooth count blade. It allows the fastest feed rate but when cutting soft, thin stock, reduced feed rate increases the cuts per inch and effectively make the blade cut like it has more teeth.