I went to the dealership to buy a 118d as I like the diesel power delivery and my last few cars have been diesel. My commuting car is a VW 2.0CR Tdi
Or that's what I thought.
I drove a 116i by accident, I wanted to try the sports seats and the dealer took me out and I thought wow what engine is this.
Anyone who thinks the 116i has a week bottom end and mid range hasn't driven one.
After that I had extended test drives in the 118d and 116i.
Yes both cars would be neck and neck in race as the performance figures suggest.
It's the way both cars go about it that is the big difference, the diesel has limited pull below 1500rpm and doesn't really get going until just before 1800rpm and then there's the usual diesel shove but by 3500rpm you can feel it's given it's best and things are getting really vocal. You can surf the torque if you keep the engine in it's 1750rpm-2750rpm sweetspot but it's hardly fun and the engine note is really gruff if you're above half throttle.
VAG's 140/170bhp 2.0TDi Common Rail diesels are more refined and have a more linear power delivery.
The 116i's performance is similar but it's refined, pulls cleanly from 1000rpm, torque delivery not as strong as the diesels at it's peak but is pretty constant throughout the rev range and you don't really feel it tailing off until after 5000rpm. You can rev it past 6000rpm but there's not much point to go beyond 5500rpm. Auto model's change up at 5900rpm in sport mode. Push hard and the soundtrack is just enough towards sporty as not to be bland but don't expect a mini M135i soundtrack. We also felt the petrol felt quicker and more responsive.
Two different ways of delivering similar performance, the petrol car is the most enjoyable when you want it to be and the most refined. The diesel is more efficient but £2k more expensive. The diesel's better resale value makes the PCP deals closer than you think. The diesel is £90 cheaper for road tax but is two groups higher insurance. (UK Costs)
So you have to chose which you like best and how the finances stack up for your mileage.
One things for sure swapping one for the other isn't worth the cost to change.
And to the poster comparing a 118d to a 125i it's torque at the wheels that determine how fast you accelerate so as well as engine output you also need to factor in the gearing. By 2800rpm the 118d's torque is already falling away sharply, the 125i' is still producing maximum torque at 4800rpm and still has 80% torque at 6000rpm This allows the 125i to take advantage of the gearing as revving allows it to stay in a lower gear much longer and thus multiplying the torque at the wheels. Even in gear times are far quicker in the 125i as the petrol has 20% lower overall gearing and thus 20% more torque at the wheels in any given gear.