When it comes to suspension parts, I would stick to Lemforder if you do not want to do the work twice. Meyle said that they changed the design of their arms... I do not trust that company anymore.
The Aluminum control arms is designed to lower the unsprung weight. http://en.wikipedia.org/wiki/Unsprung_weight
Basically if you don't plan on driving the car super hard or on the track, you will probably never see the difference.
As for thrust arm bushings.... nothing (urethane being the worse) works for the track. So we will start experimenting with modified M5 bushings and maybe spherical bearing homemade bushings.
'85 Euro 635csi Race Turbo, megasquirt, Group A
'92 525i Touring 5 speed, 3.46 diff, UUC 8.5lb flywheel, soon to be turbo.
'02 Subaru WRX Wagon with STI springs, bigger sway bars