Well obviously Reaper is a more capable platform than light aircraft - it also costs several orders of magnitude more, and is designed for an entirely different role.
Reapers do not cost several orders of magnitude more. In fact to cover the same task they are almost certainly cheaper as you need much less numbers. The cost is all in the payload.
I thought the particular role we were discussing was support of troops on the ground in current theatres (as it is part of the Nimrod role)?
Why follow the American example and use a sledgehammer to crack a nut?
I think if you offer the troops on the ground the choice, they want the capable platform with weapons on, not some half-arsed light aircraft. And I really hope that the UK aspires to provide a better capability than the Iraqi air force.
And most of all I would rather lose 10 Reapers than 1 manned aircraft.