All synthetic fertilizers are salt whether they are liquid (dissolved in water) or granular.
Ammonium sulfate = salt
Potassium sulfate = salt
Potassium chloride = salt
Magnesium sulfate = salt (Epsom salt to be specific)
Sodium phosphate = salt

With all synthetic fertilizer it must be dissolved in water before the plants can use it. With granular it must be watered in before the first dew hits it. When you water it, it becomes liquid fertilizer...much like the liquid you are considering spraying on. When the liquid dries, it becomes a dry fertilizer like the granular.

Generally it costs more to ship water around the country so liquid fertilizers are more expensive. The cost is lower because to keep the grass green, you have to apply every week or so. With fertilizers it is pounds per 1,000 square feet that matter. Dry ferts go on at about 1 pound per 1,000 square feet (plus or minus) and last quite a long time. Because 90% of the weight of liquids is pure water, it is much easier to apply 1 pound of dry chemicals than it is to apply 1 pound of liquid chemicals.

Getting to the roots faster is not necessarily a benefit. Millions have been spent to find ways to slow down the absorption of fertilizers to the roots. To claim a benefit of speed is sort of a freaky claim. The problem is when you force feed a plant you can burn the roots. The amount you use and the concentration makes the difference. If you are not experienced with application of liquid ferts, I would stick with the tried and true granular. Use a good granular ONE TIME in the LATE SPRING and two times in the early and late fall for best results. Use the ones being sold for the season. Skip over those with weed controls mixed with fertilizers.

Some clarification,
First, the kind I am using is in small bags, that you mix with water (not salt) that I guess is like instant. I do see similar brands like Jacks.
Second the recommended brands of Granular for fall like Scott's are high in N, which my understanding you don't want for fall. Up-Down- All around, you want higher middle and last numbers. Everything the Big box hardware sell for fall is High in Nitrogen, that seems like a waste. Perhaps the folks in the Composting forum (which is my regular haunt and what i normally add to may lawn), will have some in site.

I think you are mistaken about nitrogen in the fall. I'll let the others find this and comment; however, it seems to me that they recommend only nitrogen in the late fall.

The Miracle Gro Garden Feeder is a dry product that dissolved with the water used to apply. It covers 400 square feet and needs to be repeated every 2 weeks.

{{gwi:121192}}

My understanding is that the research that supported using a "winterizer" with high middle and last numbers was done in areas with warm season grasses. Recent research shows that the main nutrient your grass needs in the fall is N. Depending on where you live, how the lawn has been fertilized in the past, etc, you may never need P and K. The soil around here is naturally high in P and K, so it's a waste (and can add to pollution) to use something that has any P and K at all.

First, the kind I am using is in small bags, that you mix with water (not salt) that I guess is like instant. I do see similar brands like Jacks.

Makes no difference it is still salt. Read the product content label and see where it is getting the nutrients. Do the list of ingredients end in letters "ates" or "ide"? if it does, it is salt.

Only thing you are doing is paying about 30 times more for the liquid version vs the dry types that come in 40 and 50 pound bags. For example a very popular water soluble product, the Green Box Brand is 1.5 pounds of 24-8-16. That is enough to cover roughly 250 square feet. So to compare apples to apples cost you $60 per 1000 square feet

Now to compare to say a 50 lb bag of Lesco 24-8-16 cost $27 and covers 12,500 square feet. That works out to $2.16 per 1000 square feet

But hey it is only your money, not mine, so go right ahead and spend it.

In my area the Feed stores all sell and recommend something with like 0-20-10 but no to low N.
But the Hardware stores offer the opposite for Fall Fertilizer.

Where do you live berryman? Soils are different in different places. Maybe we can figure out the reason you're getting conflicting advice.

Clarification
After asking more about what was in my instant fertilizers I tried- want to use, they are organic, substitutes to normal fertilizers. For the Nitrogen, I will try in the spring, contains a processed of some way Urea, which for my lawn is fine. After he explained why plants can use things that are more natural and don't have to expend extra energy to transform or break down them down like the store bought stuff and that the organic can have the same effect in the end, but is less costly, makes sense. For me if they have the same results (with addition of the compost I am adding) with only needing to invest in a large sprayer, it would be worth it.

Midwest dchall