Does milk matter to achieve the perfect latte?
Barista here, and yes you are 100% correct milk does matter when making the perfect latte.  When you look at the latte, the milk makes up at least half of the beverage. Not only does it enhance and add to taste, it is a very visual medium through latte art. 

The key to great milk in a latte lies primarily in preparation, you need to heat and handle your milk correctly. 

Now to answer your question about specific milk options. First rule - BUY ORGANIC. Fresh milk from healthy cows is always going to be the superior choice. If you live in a rich agricultural area where fresh milk is available, it is a compulsory choice when making a great latte.

Second rule - more fat less heat. A simple rule, if you are dealing with thick and delicious fresh cream milk, you will need baseline heat. 150 Farenheit. Once you use the low fat milk options, you will need to increase the heat ever so slightly. Never over 175. You want silky and glossy, and adjusting heat to milk fat is an important part of the process.

At the end of the day, a latte will be delicious with any type of milk if prepared correctly. Just treat the milk with care, and buy organic where available, and you will enjoy a delicious cafe latte.