of course you know what i'm going to say about which one is best.
i don't think there is any large difference in performance from one driveshaft to another it's just a preference. hopefully some other guys will chime in and give you some feedback on mine andthe other brands.some do not work with autos and if you are crazy low (2" or more) then you will have to do some measuring to find one that will fit.

 

I don't see how you guys are running 4 inch shafts if your car is lowered 1.5 inches or more. If you have the pinion angle even close to correct it should be hitting the top of the tunnel. My Denny's is allready close to it. I guess you could set your pinion angle completely opposite of the transmission flange angle, but from everything i've read that will cause more vibration than setting it equal or rather .5 to 1 degree down from equal.

I've also read that aluminum absorbs vibrations better than steel. So that's a plus for the aluminum shafts. The best compromise is the 3.5 inch aluminum shafts, IMO, but they still want $700 for it.

 

the one i use starts at 3.5" then about 10" or so it increases to 4". i've tested this with different ride heights and pinion angles. the only time i had a clearance problem was when i lowered it over 2"(i have coilovers so i tested it in various positions)and still had stock rear suspension(control arms). once i changed the UCA and LCA's it was fine even at that level. itell everybodymore than 1.5" lowered you really need to check things cause it is close. the difference between the 3" and 4" shafts is really only 1/2 inch as far as clearanceon the top of the tunnel goes. there is no doubt it is close but i've had mine in for over a year and never had any clearance issues. i've heard of people bending the tunnel with a hammer to gain clearance but noby that has one of mine has had to do that or at least they haven't told me about it.
as far as pinion angle i found it works best at -2 degrees even on street cars although even when my car was stock(other than a tune) i had no vibrations or clearance issues. i have no idea what would happen if the pinion angle was set at +angles....it would probably vibrateyour butt off.

 

n/t

 

Spyder, still have any driveshafts?

 

yep. i'll pm you with the info. $479+shipping

 

Ive had one of SPYDERS drive shafts in my 06GT for about 3 months now with nothing but bliss from it!Ive only done the LCAs but have not lowered my car.Instant improvement is all I can say!By the way,Spyder if your looking for Drive shafts let me know!I know a guy who has a few for sale.