Anyone use M3 Competition rotors?
 

There is a 1/2" difference in diameter. Think its 14" stock for a 4.6is and 13.5" for the two-piece Euro CSL comp rotors.

Anyone know something?

Why would you want to put less braking surface area rotors on your car? If it was me, I would want larger rotors, not smaller.

Okay... Anyone else have any opinions about running a cross-drilled two-piece rotor that can provide repeated stops without any brake fade?

If the outer diameter is less with the same pad then you will have less braking surface area, so therefore less braking. Also, are the two piece rotors the same offset? If you want improved rotors just go with a two piece 14" that fits the stock calipers.
Most upgrade to the 4pot stop tech or 8 pot Brembos and don't stick with the stock calipers.

I've yet to do the swap, but comparing parts from www.realoem.com I've found that the E38 740 and E53 X5 use the same brakes. I've went ahead and bought 750iL brakes from a junkyard (calipers, rotors, caliper hangers, lines just in case, pads) and plan on swapping them into the X5. Front brakes dual piston w/ larger rotors and pads, rear gets upgraded from a solid disk to a vented disk.

I'll give you my opinion. Unless you plan on racing your X, it's all just for show. Based on your lack of information in your post, one can only guess that you intend to replace rotors on a 4.6. If that's the case, you are throwing money away. The OEM rotors for a 4.6/4.8 are insanely huge and will stop these big SUV repeatedly with no fade. Save the money for airbags and suspension bushings.

I think that's a step backward.

With those rotors you have less swept area, less mass because they are smaller, and additional reduction in mass because they are cross drilled.

All things being equal they will reach threshold temps faster.

Just curious, in what situations do you feel the stock 4.6is brakes need improvement? I think they do a great job in anything I will ever need to do in the city or highway. I have not tracked one yet though.

Here's an interesting tidbit...

A 2002 X5 4.6is took one foot LESS to stop from 70mph than a 2013 BMW M5.

Pretty impressive considering the M5 weighs almost a thousand pounds less AND has 6 pot brakes in the front.

BMW X5 4.6is - Short Take Road Test - Car Reviews - Car and Driver

2013 BMW M5 Road Test – Review – Car and Driver

Stopping distance is a function of the tire's contact area.

Repeated stops.... go with more mass. 4.6 rotors.

That's true if the car is skidding