Please help me choose between S1 and S3

Hello,

I have the difficult task of picking between Series 1 (5 doors) and Series 3.
The price is similar.

The two cars are similar in features: new, automatic transmission, leather interior etc.
Price is very similar for both.

Where they differ is optional features and engine.

S1 has 116i (136HP, 1598 m3), S3 has 316d (116HP, 1995m3).

S1 also has a few extras which are:
Navigation, parking sensors, rear camera, rain and automatic control of headlights.

Again, the price is similar.

Which should I go for? Things like parking sensors I can also add to S3, however the navigation is more costly because it already has the radio option on it.

Thank you.