The summary from a study is
Creatine monohydrate supplementation has been consistently reported in the literature to increase muscle phosphagen levels, improve repetitive high-intensity exercise performance, and promote greater training adaptations. Moreover, it has been found to be a stable form of creatine that is not significantly degraded during the digestive process and either taken up by muscle or eliminated in the urine. No medically significant side effects have been reported from CM supplementation despite the widespread worldwide use and the regulatory status of CM not being well established. Conversely, the efficacy, safety, and regulatory status of most of the newer forms of creatine found in dietary supplements have not been well established. Additionally, there is little to no evidence supporting marketing claims that these newer forms of creatine are more stable, digested faster, and more effective in increasing muscle creatine levels and/or associated with fewer side effects than CM.
There is a conflict statement per Conflict of interest The authors declare that they have no competing interests. AS is fully employed by a US trade association representing the dietary supplement industry.
This is essentially replicated here but the relationship between industry and the research team is a bit clearer
RBK is a co-founder of the International Society of Sports Nutrition (ISSN) and has received externally-funded grants from industry to conduct research on creatine, serves as a scientific and legal consultant, and is a university approved scientific advisor for Nutrabolt. (and on it goes)
However the Mayo Clinic is generally disinterested and factual.
Creatine might benefit athletes who need short bursts of speed or muscle, such as sprinters and weight lifters. While taking creatine might not help all athletes, evidence suggests it generally won’t hurt if taken as directed.
The American Pharmacists position is also clear albeit possibly somewhat self-serving…
While creatine may enhance the performance of high-intensity, short-duration exercise, it is not useful in endurance sports. Because commercially marketed creatine products do not meet the same quality control standards of pharmaceuticals, there is always a concern of impurities or doses higher or lower than those on the labeling. Consumers should balance the quality of information supporting the use of creatine with the known and theoretical risks of using the product, including possible renal dysfunction.
There are myriad internet sites from the scholarly to business to the self serving touting creatine. The overall consensus reflects that of the Mayo Clinic and American Pharmacists pages. The first two citations above are referenced a seriously large number of times, possibly making themselves ‘self proving’ from those citations, or perhaps sufficiently rigorous.