My wife and I went and test drove the X1 and we were not impressed. Too small and noisey. Then we drove the X3 and were sold. We have one on order now waiting for delivery sometime towards the end of this month. I believe the small difference in price of the X3 is well worth it.

 

In my experience the seats in the X3 are much more comfortable than the seats in the X1. A long trip driving the X1 would not be pleasant for me. Consumer Reports gave the BMW X1 front and the rear seats a 3 out of 5 rating for comfort compared to 4 out of 5 for both the front and the rear seats in the X3. YMMV.

 

There've been a few occasions where our 2013 X3 returned to the dealer for service when it was under warranty and they provided an X1 loaner. Other times it might be an X5 or another X3.

Moving the two massive Peg Perego toddler seats in and out of the X3 is now muscle memory... so I found it interesting how there was a bit more maneuvering that had to be done to fit these seats into the X1 loaners. The door frame of the X3 permitted the seat to pass through with zero issues. The X1 required a bit of Tetris skill. Certainly a notable space difference between the two. With both Peg Perego seats anchored in place, the X3 offered more space in the gap between the seats.

Your observance of interior measurements mirrors what we had pondered back in 2013 when deciding between X3 and X5. The published numbers seemed to indicate that interior between the two were nearly indistinguishable and it wasn't entirely easy to tell sitting in each for ~5 minutes. Once the familiarity of being in an X3 has set in, it's been much easier to sense the size differences going down to an X1 or up to an X5. The immediate driver controls on all three are in very familiar points in space... so not TOO much difference reaching for steering, radio, shifter, foot pedals. The size difference comes in other ways. In the X1, reaching for the passenger door pull handle is considerably closer compared to attempting to do likewise in the X5.

If you're also bringing up the point of safety, it might be worthwhile to point out chassis height across the X series. The identical set of toddler seats we put in our 2013 X5 shows that those seats end up in a location higher than the X3. There's also a larger gap of space between the seat and the outter door. If this is observed between our X3 and X5, I'd presume the obverse would be true moving down to the X1.

Our X3 and the loaner X1 share the same N20 twin-scroll turbo 4-cyl and I presumed the X1 ought to feel more lively since the chassis should be lighter. Getting it on the highway and launching it from a stop, this was NOT the case at all.
The X1 felt it lost a notch of nimbleness I was accustomed to in the X3. Steering response? Suspension geometry? I couldn't quite put my finger on it. My times in the X1 loaner only lasted a couple days, but every time I got in one, I'd wish the service dept would finish work on the X3 soon.

 

The BMW X1 has a slightly less powerful (228 HP) 2 liter 4 cylinder engine than the X3 (240 HP). The X1 employs an Aisin transmission whereas the X3 uses a ZF transmission. The X1 is derived from a FWD platform whereas the X3 is based on a RWD design even if both vehicles are offered in the AWD versions. These mechanical differences may account for some of the performance difference observed by CarterTG.

http://www.bmwblog.com/2015/08/07/what-should-i-*****the-new-bmw-x1-or-x3/

 

The newer gen, smaller X! has a wee bit more engine performance. is quicker and gets better gas mileage.

BMW X3 sDrive20i Urban:
4 cilindros BMW TwinPower Turbo / 1997 cm3 / 184 hp (5,000 - 6,250 rpm) / 270 Nm (1,250 - 4,500 rpm)
0-100 km/h: 8.2 segundos.
Combinado: 14.9 km/l (*)

All New BMW X1 sDrive20i Urban
4 cilindros BMW TwinPower Turbo / 1998 cm3 / 192 hp (5,000 - 6,000 rpm) / 280 Nm (1,250 - 4,600 rpm)
0-100 km/h: 7.7 segundos
Combinado: 16.9 km/l (*)

 

Just had 2017 X1 loaner for five days.
X3 miles better in handling and comfort.
Engine performance same.

 

Hi guys so I went for the x3, as many pointed out there are a few differences so I went and drove the 2.

Main difference and why I chose the x3 is b3cause the x1 feels a lot more like a car (not necessarily a bad thing) but I wanted a SUV.

X1 I drove is faster than the x3 has more HP and also is lighter you can feel the difference in that but you also feel it a lot lighter which I didn't like and the x3 feels a lot roomier inside.

 

Good choice.

 

Agree w/ all. Have had a brand new loaner X1 for a week (some idiot from dealership dented my rear door after some routine maintenance, so it's getting body work) . My observations after 400 miles:
- Harsher ride compared to X3 - feel every crack in road, noisy run-flats.
- Seats lack support/cushion - hurt after my 50 minute commute. Long trip may be painful.
- Hatch almost took my head off twice, when putting things in the back. Closes suddenly. Sensor or something being tripped while under there.
- Gas mileage pretty good - getting 30 or better mpg.
- Peppy, quiet engine at highway speeds, feel slight torque steer or something sometimes when accelerating. (front-wheel drive based influence?)

 

I picked up a 2018 X1 this weekend (only have about 100 miles on it so I won't go into a lot of detail comparing it to the 2011 X3 that we have).

I'll say this - the rear seats in the X1 are much better. Why? Because the option for reclining/sliding rear seats makes a world of difference. Being able to recline is awesome. We also optioned the front sport seats, which are narrower than the X3 sport seats, but still comfortable (again, havent driven the car much, 10 miles was furthest in one sitting so far). Our local dealers (3) had maybe 10-20 X1s each on their lot at any given time. Usually 1-3 had sport seats, and 1 had sliding seats. Seem to be rare option selections for dealer stock but 1000 times worth it.

 

I picked up a 2018 X1 this weekend (only have about 100 miles on it so I won't go into a lot of detail comparing it to the 2011 X3 that we have).

I'll say this - the rear seats in the X1 are much better. Why? Because the option for reclining/sliding rear seats makes a world of difference. Being able to recline is awesome. We also optioned the front sport seats, which are narrower than the X3 sport seats, but still comfortable (again, havent driven the car much, 10 miles was furthest in one sitting so far). Our local dealers (3) had maybe 10-20 X1s each on their lot at any given time. Usually 1-3 had sport seats, and 1 had sliding seats. Seem to be rare option selections for dealer stock but 1000 times worth it.

It seems your hot button is the reclining/sliding seats in the X1 but you are comparing a 2011 vs 2018. For me, the X3 is much larger and doesn't need a rear seat that slides. The reclining feature may be nice on a long trip, but I'm usually driving and my wife is in the passenger seat so neither of these features are high on our list. Also, the standard equipment in the X1 seems lacking compared to our X3, but I suppose the same thing can be said comparing an X3 to an X5.