There are a couple of ways that testosterone esters vary from one to the other, but not limited to:
- Test Prop is less HPTA suppressive than long ester test. In a 2020 mouse study, test prop was found not to be as LH/FSH suppressive as cypionate or enanthate. Testicular weight was also higher. Anecdotally, I notice larger loads on test prop and prefer test prop for hrt/cruising.
- Test Decanoate is found (anecdotally) to cause less hair shedding. Likely due to its slower release having an impact on dht conversion, but that is speculative. In my own experience, longer esters in any AAS have fewer androgenic sides than shorter esters, so there could be something to this. For example, I barely feel tren e, I get next to zero of the neural drive that I get from acetate. Acetate also potentiates more aggression and acne issues than enanthate.
- I notice that with test prop, I have a lower ceiling for estradiol levels, meaning, if I inject 50mg test prop per day, my estrogen levels will be significantly lower than if I inject an equivalent dose of enanthate, like 2-3x higher. This is because prop has a faster clearance time and in turn less saturation. A high amount of test saturation is also correlated with larger day to day variations in estrogen levels. This is also seen when using npp vs deca. If you were to inject 350mg/week of nandrolone decanoate and 350mg/week of test enanthate, your estrogen will probably be off the charts, you will have ed sides, it's gonna be a mess without estrogen control. However, if you were to do 350mg/week of NPP and 350mg/week of test prop, that would be much more manageable from the estrogen and side effect management part of it, because of the lower saturation amounts.
All of the above is from different studies that I've read, with varying levels of robustness OR it is based on anecdotal experience so don't take it with caution. My experience with AAS won't necessarily be the same as yours.