First of all X1 came out at 2009 so it is a 4 years old design not 6; still it is using an older platform than the F30.
Almost everything on the new F30 3 series are better than X1 except the steering. Every new BMW (also X1 S-drive) using the electronic assist steering which drawn bad criticism; X1 X-drive still use the good old hydraulic system.
"The X1 costs less but you get a lot less"
True in some way, the price different between the base X1 28 and base 328 are about $6k. You do get iDrive standard on 328 plus Xenon light and backup camera aren't bundle with other stuffs; IMO it is still a big price different. To keep the cost down on 3 you need to step down to the new to US 320i but you lose 60hp on the same engine with the same mpg.
If you don't mind the steering and the extra cost; get the 3; it is a very nice car.