"Im not an electrician, but I try to play one on BYOAC"

Depends on the length of the run and if your going to have additional outlets. If it is a substantial length, then use the conduit, put some junction boxes with blank covers for future use. If it it like 5' or something small like that, then I wouldnt use conduit. Also, depends on how clean you want it to look as well. Also, if you just run the wires, you do have a chance of risk of nails being accicdently pounded into the wire (from the outside walls or roof) that could cause a fire or electricution (hopefully the breaker box trips before this happens). 1/2" conduit in the US is only $1.50 for a 10' section and maybe $.45 for each coupler, maybe $1.25 for junction/outlet box, 125v 10-20amp (standard)outlets are like $.75, covers are like $.50ea, so for the extra few $$$ I'd run the conduit!
Fordman