Flat Roof verses Pitched Roof on extension

[fastliving]

Can anyone add to my pros and cons?

Flat Roof
Pros - cheaper
Looks more 'neat & modern'
Cons -
Higher insurance
I assume maintenance? Does a flat Roof need replacing frequently?
Problems with water pooling/leaking around sky lights
Leaves/moss etc on skylights

Pitched Roof
Pros - pretty maintenance free
Cheaper insurance
Higher ceilings
Cleaner skylights
Cons - more expensive
Takes up more room on your house exterior, looks unbalanced?

Anything else, am I missing something obvious?

Does anyone have an idea of what the difference in cost is between the two?

A flat roof extension would put me off buying the house.

Flat roofs done properly have a reasonable life but don't quite reach the forever standard of concrete tiles. They are also easier to get wrong.
They should have a fall of 1 in 40 or better and a strong structure and boarding to avoid any sag.
The old roof coverings were quite low tech but now we have all sorts of modern materials so you can even do it yourself if you feel you can do a better job.
The main concern is detailing, any edges abutments and penetrations need dealing with properly with lead or the correct proprietary seals but that doesn't always happen.
Also any coping stones on top of parapet walls should fall to the inside to avoid staining any render or causing water penetration.i think they're called once weathered, the correct stones to use.

If you have a parapet around the roof, be very careful about drainage! The “guttering” drainage channels are often hidden and can get blocked - they are difficult to clear.

Flat roof extensions generally look hideous.

My late parents' house had a flat roofed extension and my PILs have one too. Both were/are no end of trouble. I appreciate that isn't a large sample but it is enough to put me off! Unless you live in a hot, dry country, I would go for a pitched roof personally.