I would say both. It also depends on how thick you lay it on....how many layers/other products above and below it etc. I didnt realize you were in BC but if I had to choose one product I would say Dynamat or Damplifier Pro.....or something along those lines if you can get it. Use the butyl rubber stuff and not the asphalt impregnated ones.
They will give you both heat and sound suppression. The Damplifier Pro does both as it has a fairly thick foil shield on it....it cost me about 8 bucks a sheet. And you can always lay down a layer of the less expensive foil faced padding over it for a little extra....I think I paid about $30 for a roll of that. Regards.