I am a former 1.3 AMT Pulse owner, only got rid of mine as she crept over the 100,00 mile mark and didn't want to worry about future costs - that aside it was an awesome car.
Having driven a 450 the gearbox is shocking but the 454 box is a vast improvement. Its the same 5 speed manual gearbox in the forfour, it has a few extra gizmos plus an overdrive giving it 6 gears. The 1.3 is the average engine, as in, it gives good power delivery, superb mpg and decent insurance.
As for the diesel v petrol argument, take a 55 plate VW Polo 1.4TDi and compare it with a 1.3 smart forfour... both will do 55mpg but what is cheaper to buy at the pumps?
Diesel no longer has the pull for the average driver, it costs too much to fill up and now many petrol engines give the same tax breaks and returns on fuel.
To the OP, the Pulse is an adequate spec for a car it will do the job - you'll more likely find the larger engines in a Pulse (cheaper trim level) than the Passion, the Passion you'll find the 1.1 and CDi engines, more expensive trim level so people scrimp on the engine.