Vacuum tube panels or flat plate?

Currently in the solar thermal panel market there are 2 types of solar thermal collector (panel) - vacuum tube (or 'evacuated tube') and flat plate collectors.

It is widely accepted (and supported by a DTI test report carried out in 2005) that vacuum tube panels are up to 20% more efficient than flat plate collectors. They tend also to be more robust in their build as well as easier to repair should a fault develop. But, they come at a higher premium than flat plate collectors and, in some people's minds, there is also a question of aesthetics. So, what are the pro's and con's of each?

Flat plate collectors:
Pros are:
- cheaper to purchase.
- aesthetically more pleasing to the eye (especially the 'in roof' varieties which can look like Velux-type windows from a distance).

Cons are:
- heavier to install (thereby potentially increasing installation costs).
- if any part of the panel is broken, a whole-panel replacement is required.
- less efficient than vacuum-tube.
- a greater collector area is required to match the same energy output as a vacuum tube collector.
- dirt collects on the panel and over time reduces efficiencies further.

Vacuum tube collectors:
Pros are:
- light and therefore easier to install (hence reducing install costs).
- if one of the tubes breaks or fails, tube replacement is simple and cheap (the whole panel does not need replacing).
- more efficient than flat-plate collectors by around 20%.
- faster response times.
- smaller collector area required to match energy output of flat-plate collectors.
- stay clean given the cylindrical shape of the tubes. Hence efficiency of panel is maintained.

Cons:
- higher initial cost - however, over the life-time of the product, vacuum tube collectors will return a better cost/annum given their longer life expectancy.
- aesthetically not so pleasing. However, they do 'announce' the household is environmentally responsible!