The old long strut flexes and makes for a somewhat uneven DA pull especially with heavier mainsprings. They came out with the short strut and plastic base to solve the flex issue. The E2 has yet another strut and base design in order to clear the E2 grips. The downside is the strut binds so going to "standard" grips would allow the E2 strut and base to be replaced with the "standard" short strut and plastic base.
FWIW, I run a 17lb mainspring with 2 coils removed on my 2 GGI X5 Allrounds. I remove the 2 coils because the Wolff spring would coil bind at its stock length making the end of the trigger stroke a bit stiff as it pushed coils over top each other.
I ran into the coil bind problem with Wolff recoil springs as well. I run a 14lb Wolff recoil spring and I swapped one out right before a match. All match long my brass was barely coming out of the ejection port and bouncing off my hand. I later discovered that the Wolff spring I had put in the gun before the match had 4 more coils than the one I had replaced. I checked slide travel and found that the longer spring was going to solid coil bind limiting travel to a shorter stroke than with the factory recoil spring. 9mm minor loads don't have enough recoil to compress the stiff secondary spring on the X5 so my slide was going back barely enough to eject the case.