Two reasons:
That's over 17% less actual tren with enanthate
With enanthate, not only do you get less tren, you don't know or have as much control over its release. Say the enathate relases over a 7-day period. Is that release the same amount every day, or like 10, 20, 30, 20, 10, 5, 5 (just an example-not fact). With that long a time period for release and uncertainty of when, I chose to use faster acting esters or no ester.
xcel