Depends on what are your experiments,

however as already answered by few of our friends

cow dung is good booster and enhances the soil as it is also called as a fertilizer itself due to its NPK values but Chicken Litter will have more nitrogen compounds.

Depends on whether you are adding the fresh dung/litter or stored one

Both are good in their own way, but one advantage of poultry manure is that since nitrogen is excreted in crystalline form (as uric acid), the nitrogen levels do not deplete/disappear as quickly after spreading on the field.

У птичьего помета больше потенциала ! Если он используется в качестве удобрения для почвы. Птичий помет больше содержит питательных веществ и микроэлементов по сравнению с коровьим навозом.

Dried poultry manure is two to three times as rich as cow manure in inorganic fertilizer content. Poultry droppings are better manure than cow dung (or other farmyard manure) in nitrogen, phosphorous and potassium content, the elements most deficient in Indian soil. https://www.poultryworld.net/Breeders/General/2006/12/Poultry-manure-makes-better-fertilizer-than-cow-dung-WP000845W/

Composted cow manure fertilizer makes an excellent growing medium for garden plants. When turned into compost and fed to plants and vegetables, cow manure becomes a nutrient-rich fertilizer. It can be mixed into the soil or used as top dressing. Most composting bins or piles are located within easy reach of the garden. https://www.google.com/search?q=cow+dung+vs+poultry+manure&client=ucweb-b&channel=sb

Poultry droppings are better manure than cow dung (or other farmyard manure) in nitrogen, phosphorous and potassium content, the elements most deficient in Indian soil. Poultry produce about twice as much fresh dropping (on a wet-weight basis) as fuel eaten. Birds consume about twice as much water as feed. A laying hen produces about 227 gms of fresh dropping (75% moisture) daily.

Poultry litter also may be converted to compost litter and used as animal feed. In animal farming feed usually represent 60% to 70% of the total expenditure. Its feeding value and palatability could be improve no doubt, by adding salt, other minerals and molasses. Utilizing poultry manure of feed nutrient may help to alleviate pollution problems; diseases feed costs and increase the supplies of available nitrogen and essential mineral sources.

https://www.poultryworld.net/Breeders/General/2006/12/Poultry-manure-makes-better-fertilizer-than-cow-dung-WP000845W/

Cow dung is better than Poultry manure.

It all depends on the feeding regime of each animal species. However, due to the high quality diet provided to poultry, it renders poultry manure as a superior manure.

this is because

1. poultry are monogastrics and contain less and less microbes in their digestive tracts. Microbes digest nutrients in feed making it available to the animal, as such, fecal nutrient content is low where there are high numbers of microbes.

2. ruminants such as cows have a higher feed retention time thereby taking a toll on feed nutrient status. this translates to a lower fecal nutrient content as most nutrients are accessed by the animal.

3. poultry are exposed to ad lib feeding, which translates to less feed retention time, which, hereby translates to high fecal nutrient status.

....please also note that cattle under pen fattening produce a relatively higher fecal nutrient content as opposed to those on free range.

.....also, disappointing, is that poultry manure contains an excess of nitrogen which could be detrimental to crops

.....poultry manure is not as bulky and applicable as cow dung, it takes a great deal of resources and labor to collect.

.....its expensive, considering the high value protein inside poultry manure, which could be used in crop-livestock interactions(poultry manure is a delicacy and a source of protein to cows.

Cow dung is much better than poultry manure.

Cow-dung is better than poultry manure

cow dung is better than poultry manure.

Poultry litter is richer for nitrogen compounds

I think cow manure is better than poultry one because the percentage of urea is high in poultry droppings, and this may help the plant grow larger than what is required in vegetables.

Poultry Manure is better

Poultry manure is better fertilizer than cow manure according to many field experiments. For example, please use the link:

https://core.ac.uk/download/pdf/234660759.pdf

cow dung is better than poultry manure but Poultry litter is richer for nitrogen compounds .

Having read all the answers: my main question remains what is the definition of better?

What characteristic do you give the highest priority?

Robert Renema has pointed that out in another way is his answer.

I don’t quite understand the question ? ,What kind of potential are we talking about ? ,Energy ? , Electric ? , Does it depend on what cow dung or bird dung is used for?

As dry matter, the poultry manure is better, due to the considrable amount of some minerals such as Ca,l and P quantities.

Poultry manure is better in NPK and also free from weeds

Poultry excreta is always better than the cattle manure. As in terms of potential the most important is its fertilizing potential than any other. hence poultry excreta is better than the cattle manure

Depends on what are your experiments,

however as already answered by few of our friends

cow dung is good booster and enhances the soil as it is also called as a fertilizer itself due to its NPK values but Chicken Litter will have more nitrogen compounds.

Depends on whether you are adding the fresh dung/litter or stored one

Absolutely cattle if you want to produce biogasses