More than one person has suggested the 2.4 was a bit better blower.
Actually he's not a fan of either one (Twin screws in general). Thinks factory tolerances should be tighter on 2.7. Believes you should stay 2.85 pulley or bigger for reliability on 2.7 unit.
These are my thoughts/words not his: If you look at the rotor length on the 2.7, it's substantially longer than a 2.4, like 1.2" at least. I know the Metco tool adapter was 1.4" to make up difference on the RE snout so maybe its 1.4". Now you have that much
more mass and length spinning at speed (like 18000 to 22000 on the slower bigger one, the smaller of the two is
faster). When the blower was designed, it was designed, period. Now Dodge wanted bigger and better. What's the cheapest route? Stretch the existing design. But then it's not a properly designed clean sheet of paper kind of thing. So I'm thinking more flex when stressed? Leading to bearing/rotor/wear problems and weird noises?
Best example is this. (I'm originally a Chevy guy so forgive me). When Chevy designed the
original 396/427 BBC it was the perfect design unto itself. That motor will spin to 7000 plus RPM seamlessly and vibration free almost like a SBC and was
internally balanced. Rod /stroke ratio excellent, crank pin overlap excellent. Then Chevy wanted more cubes and more torque and H.P. What'd they do? Stretch the existing design. Yep, the 454 makes more power. But all the race/street guys knew it was less reliable. Rod/main knocks real common. Thrown rods, real common. Going 7K+ repetitively forget it. Now you
could get it to live (I did it) above 7K but you needed all the best reinforcement. 4 bolt mains, nitrided forged crank, big rods etc. And I'll tell you this; even with my 454 (which never failed) There was a vibration at @2500RPM when coming down off high RPM because with the now
externally balanced crank and longer stroke there was more overlap and torsional flex and the machine shop could only build perfect balance at high or low rpm but not both.
So until they come out with titanium rotors and a more heavily reinforced T6 case, I'll keep my 2.7 pulley at 3.17 dia. and be happy with the power...I hope.