Kefir, or kefir milk, has a few advantages over yogurt.
First of all, and that's what allowed me to start doing home-made kefir, is range of temperature required. Kefir requires what's called a mesophilic fermentation, in the range of 18 to 30 °C. This means it can be done in most home environments, differently from yogurt whose fermentation being termophile requires a 40°C temperature, not usually available at home. Quick & easy, even if we are pretty busy.
Now with minimum effort, a good organic milk, a freeze-dried bacterial mix as a starting culture (available in most health food stores), a couple of one-pint glass jars, I have a very good product which costs me in Europe about 1.3 dollars a quart, since I can use kefir to start successive cultures. Commercial organic yogurt here ranges from 3 to 6 dollars a quart. It's good to keep a few dimes in the pocket, given the costly nature of an healthy diet.
Another benefits which Yogurt does not carry is menaquinones or K2 vitamin. Pls choose starters which contain also lactococcus and leucostoc bacteria, these are responsible for the formation of the precious vitamin K2, which may be found in a certain range of values in kefir products. According to Manoury et al., 2013, this is from 1 to 25 micrograms/dL, excluding the lower value and the higher values (probably a drained Polish kefir or Tworag). Not much but, assuming an average most likely value of 2.5 microg/dL, with half a liters we have 12-15 micrograms which is a little which can be added to cheese and make up a minimum natural intake of K2.
The gel-like (pudding-like) consistency of kefir is due to kefiran, a plysaccharide which has some interesting properties like transforming galactose. Like Yogurt, Kefir is far more digestible than milk. This morning I ate 750 ml (3 cups) and am pretty much good. The same amount of milk would have cause unordinate fermentation and bloating in my stomach.
The various bacteria contained in kefir have many protective properties which are listed in
this recent scientific paper from Prado et al., 2015.. reducing cholesterol and protection from tumours are a couple of examples.
Galactose in kefir is turned into lactic acid and ethanol (alchol), that's why probably is well tolerated even by those untolerant to milk.
The disadvantage: kefir contains a small amount of alcohol, up to 2%.