I'm currently learning to drive and in the process driving two cars (the instructors, and my parents for extra practice). Both are small 1 liter cars (petrol).
What I've found is in my instructors car, I can quite happily pull away on a steeper hills (let's say a T junction on a slight incline or stop start traffic on an incline) with just the clutch (no gas needed).
I find in my parents car, I would stall in these situations if I just used the clutch, and require some gas to avoid stalling, but naturally this requires using the handbrake in order to avoid rolling back when you swap from brake to gas (which isn't always a great idea say at a roundabout whereby the entrance on is a hill, and you need to be quick to claim).
Do different cars have more/less powerful clutches?