The answer to that are purely practical issues: Cost and tolerance of a particular brand. Most people are started on a brand recommended by their doctor and a dietician or nutritionist. If the feeding tube is used to supplement an oral diet, formulas available in many stores such as Ensure or Boost may be all that is needed. But these are not full nutrition and a full nutrition formula not available in stores will be needed at some point. Jevity seems to the most commonly used brand. The cost of these full nutrition brands are similar. Feedings are best begun slowly (slower drip rate if on a pump, smaller amounts per feeding if on gravity/bolus feedings). Intolerance and slow adaptation are most common in people who have lost a lot of weight and waited until oral feedings were very difficult before having a feeding tube put in. The body chemistry and metabolism has gone into what is generally called starvation mode, and it requires much more than simply feedings to readjust the multitude of problems. In short, don't blame the formula if a feeding tube was put off or refused for too long.
The cost of formulas goes up if a formula for people who also have other medical problems such as diabetes, liver or kidney problems is needed. Formulas are generally made without dairy products so lactose intolerance won't require a special formula.
The next price increase comes with "natural" formulas. The most popular now seems to be Liquid Hope. People who are intolerant of other formulas may do better with natural formulas. It requires a physician documented statement of a history of intolerance to regular formulas to get Medicare coverage for these high priced formulas, so unless you are self paying for formulas it is unlikely that a natural formula will be the first formula used. Another option is blenderizing food yourself to create a tube feeding formula. In order to prevent tube clogs, this requires a high quality blender to actually liquify the food and not just grind it up. It requires knowledge of at least basic nutrition to ensure a balanced diet containing the right ratio of protein, fats, carbs and sugar, fiber etc. Shopping and preparing the foods on a daily or every other day schedule to prevent spoilage will add to the workload of the caregiver. None of groceries or added ingredients are paid by insurance. No special diet or supplement or herbs, etc. have been shown to slow or reverse ALS. There is always a dietary fad or supplement making the rounds of the ALS community, none proven to help. Liquifying the persons normal meals can give a psychological boost to the patient, reduce the workload of the caregiver, and even improve tolerance because foods that caused problems would have been removed from the menu long ago.
And now, a personal editorial on formulas. "Natural" sounds great and is a word used to promote purchase of foods, supplements, and all health products. When it comes to food however, the body breaks everything down to basic nutrients anyway. Its only concern is how easily it can break food down to those basic vitamins, minerals and chemicals. It doesn't matter if your potassium comes from a banana or a potassium pill. Formula ingredients read like a witches brew because they list the nutrients, not the specific foods they come from. Chia seed and grape extract sound natural, but exactly what you get from them and how much is more important in developing a balanced formula. All food is made up of chemicals and using that knowledge makes formulas match nutritional needs, not advertising slogans. Few of us eat a really healthy diet to start with but switching to an all natural diet after ALS has started hasn't proven helpful beyond what it would do for someone without ALS.