[johnnydad]

We are running my M135i and my wife's E91 320d.

Front compartment in the 1er is just that wee bit narrower. I don't find it claustrophobic in any way, and you only really notice the difference where the central armrest is. The rear seat is slightly narrower also - but 3 full size adults are uncomfortable in either due to the rear wheelarch intrusion. For 4 adults, unless two of them are 185cm or above, passenger space is pretty equal.

Both rear compartments fold flat easily, both are well shaped and neither has particularly obstructive wheelarches when loading. Its easier to stow the 3ers blind when not needed but it is a heavy thing - the light parcel shelf of the 1er is less hassle in some ways. Obviously there's more space in the 3er, added to by a useful under-floor compartment. Our family of 4 can go away for a week in the Touring, or just about squeeze luggage for an overseas trip (3 large, 1 medium suitcases, 4 large cabin bags) and 5 passengers. The 1er is only able to accommodate 3 people and their luggage in such situations unless you are prepared to cram things to the ceiling.

The 3er will transport 3 MTBs and 3 large adults with an overnight bag each. While the 1er will swallow those same 3 bikes and a similar amount of paraphernalia, you end up one passenger down.

I find the 1er just about as capacious as my previous E90 325i however, and vastly more flexible for loading bikes and large items.