I tried the B150, B170 & B200 petrol, plus the B180 diesel & B200 diesel in addition to the turbo we ended up with.
I am sure the 150 will give good economy, especially the latest with stop/start.
IMHO, I found most of them rather gutless except the B200 models (petrol/diesel & turbo). I suspect you might find a B150 sluggish compared to a 2L diesel, although do not know how powerful yours is.
Depends what you're after... & of course best to test drive & compare.
In the 3k miles of ownership it never missed a beat. Primarily used as mum's taxi so speed wasnt the biggest priority. The CVT was very smooth but it enduces at lot of revs and not much action from low speeds and start offs. Once on the move things settled down nicely.
MPG was around 36.
Quality and the space offered was excellent.
Slightly strange steering when turning sharply, say at a roundabout, although i believe this is something to do with the suspension and is normal.
Overall a very good car - we just didnt realise at the time how much we needed 7 seats and that was the only reason we sold it.
2 years on and we're back looking at small mercs though this time it looks like we may opt for an A class. Touch more style (subjective I know) and not much loss in space caompared to the B Class