I am also most interested in the G10 because of its 28mm lens.
The Canon housing is fine but will not allow you to quickly change F stops and shutter speeds because there is no dial on the back of the housing for that control. If it is like the G9 you will have to use two different button controls at the same time to accomplish this. I believe the Ikelite housing has a dial on the back. The price difference is considerable between the two. Personally I would buy the Canon housing at around $270. versus around $650. for the Ikelite one.
As for strobes I have nothing against Ike strobes except they have no built-in focus/target lights. I used an Inon D-180 (replaced by the D-2000) for about four years and it had a focus/target light. I found it to be invaluable and wouldn't buy a strobe that didn't have one.
Currently the Inon D-2000 and latest Sea & Sea YS110 Alpha have built-in target lights.
The D-2000 has two bulbs with an offset target light.
The YS110 Alpha has three bulbs with a center target light.
My D-180 died on me and a friend was kind enough to give me his Sea&Sea YS90DX (no focus/target light) After using the Sea & Sea I prefer its shape over the Inon's as well as it is more buoyant than the Inon.
If I purchased a strobe today it would be the Sea & Sea YS110 Alpha.
If you don't buy a strobe with a built in focus/target light odds are you will add one and that's just another piece of equipment.