like negrogesic said, all strains contain various and comparable levels of mitragynine and 7-hydroxy-mitragynine. That's really what you are looking for.
There are also 32+ other known alkaloids in kratom strains which make them slightly different in effect and potency.
The difference is ultimately small, though.
I can tell the difference between cannabis strains easier than kratom strains.
meang da kratom compared to bali kratom is the most drastic difference and I could probably tell the difference between those 2 strains (blindfold).
I have never been able to tell the difference between "red leaf" and "green leaf" or whatever. Only major geographical strain differences... such as meang da vs bali.