The x3 IMO is the worst handeling BMW made. The acceleration is horribly slow, 8 secs for the 3.0 or soemthing like that. THe cornering is unbelivably bad, you feel like your gona roll. There very simple and not to BMW standards, but the price tells you its a BMW. We hardly ever get any in at work. I guess thats one of the plus's of them. Not many break down and/or have big problems.
Now the X5's I think are total junk. There in every day for rattle noises and other things that have broken on them. The 4.4 and 4.6's arnt bad in a straight line but dont think your gona be taking any corners fast anytime. BTW I drove my first 4.8 today. The pluses is the engine/ exaust noise. Best sound comming out of any BMW, including the M's. The straight line run is very nice with the 4.8. The corner is better then the 4.4 and 4.6, but thats is you have the adjustable suspension at its lowest point. Also anotehr nice feature but sorta pointless. Adjustable suspension, you can make it ride high like a regulaor X5 or drop it down and make it look like the AC Schnit X5. Orocurse if you have the right inside package it looks good but its still the same as all the other X5's.