I am sorry if it is obvious however what is the actual difference between the two.

what are are the advantages and disadvantages of storage combi over system for a big 5 bed house 4 bathroom and 20 radiators, no more than 2 bathrooms will be used at the same time. vitodens-222-f-35kw have 130 litre storage and will provide 18L/M pressure.

cdn.plumbnation.co.uk/site/viessmann-vitodens-222-...f

Am I right to think system boiler would give me a option of larger cylinder, let's say 300 and that would be the only advantage, of course it would be a little cheaper as well but since we have a combi at the moment storage combi might end up cheaper overall.

The flow rate of my house from kitchen tap is around 15 L/M, so if I had vitodens-222-f-35kw does that mean i get 18L/M for 130 litres then it drops back to about 14?

130 Litres would be more than enough for us specially when I know it get heated up in less than 15 min.

If you believe system boiler must be used could have a little technical details so I could understand it myself. as from my understanding vitodens-222-f-35kw is the same as system boiler with smaller cylinder that in built in.

I was told in the past combi boilers can not heat up the radiators and heat the water for shower at the same time and heating the water take priority, but does that mean the boiler can heat the radiators till 130litre depleted first?