Yes, it should put the area directly under the light in Very high light. However with the length of a 10g it might not cover the whole tank in high light. I have a similar light and the reflector seems to direct the light straight down which is perfect for cube or hex tanks.
And the other light is probably too much for the 15G.
I have 3 tanks going the two tanks with medium light run super smooth. The one tank with way too much light (2x24W T5HO on 20g high) has been having non-stop algae problems. Once I get some spare money I'm going to get something to suspend my light a bit higher.
What I would suggest doing is using that 65 watt fixture and suspend it maybe 6 inches above your 10G and use it to light both tanks.