When to use a tin of tomatoes -v- passata?

I am still relatively new to this cooking from scratch business (it wasn't that long ago that I thought heating a ready meal constituted cooking!) and was wondering today what would be the main difference when using tinned tomatoes or passata?  Will it taste different or will there be a different consistency?

For example, I have now got into the habit of making a vegetable curry on a Sunday and eating it during the week.  I use a tin of tomatoes, but today saw some passata in the supermarket.  Would it make a massive difference if I used that instead?

Thanks 

This is a recipe based on one from the River Cottage book of Preserves.
Its well worth the effort. You can obviously change the seasoning to suit your taste.

Cut tomatoes in half and place them cut side up in oven dish or baking tray.
Cut up (big chunks) some shallots or onions & mix in with toms. Add 3-4 garlic cloves thinly sliced. Then drizzle over about 50ml of oil. I use olive but sunflower or rapeseed is also good. Then sprinkle over rosemary, basil & oregano. I used dried because I didn’t have fresh. Then sprinkle on salt & black pepper.
Roast in a pre heated oven (180c/gas mark4) for about an hour or until toms are very soft. Push toms & all juices through a sieve into a saucepan or maslin. Then bring to boil & place into sterilised jars. Seal the jar straight away.
Then place jars into a large saucepan & cover with warm water. Don’t forget trivet or tea towel on bottom of pan to stop jars breaking. Bring up to simmering point (88c) over 25 minutes then simmer for 10 minutes.
Remove the jars and allow to cool. They will have a shelf life of about a year.

1kg of tomatoes fills a 1lb jam jar.