A quick thoguht ..

[wgp1987]

When it comes to using a flash for fill light for mainly subjects that will be 5-10 feet away do you really need the most powerful flash? Can having a large flash not hinder your ability to take a properly exposed photo as much as it could help?

 

[kundalini]

Fill flash on your subject should be only strong enough to kiss the subject with enough light to remove any unwanted shadows (raccoon eyes, etc). Dial down the power setting so that it's not seen as obviously flashed.

 

[wgp1987]

Fill flash on your subject should be only strong enough to kiss the subject with enough light to remove any unwanted shadows (raccoon eyes, etc). Dial down the power setting so that it's not seen as obviously flashed.

Covers the 105 range?
Nissin | Di622 Digital TTL Shoe Mount Flash for Can | ND622C

 

[Dao]

If you stop down the lens (i.e. smaller aperture) and want to have a overpower the sun type look photo. You may need to have a powerful flash or flashes. (On or off the camera)

Search "overpower the sun flash" in flickr will give you some example.

 

[myfotoguy]

When it comes to using a flash for fill light for mainly subjects that will be 5-10 feet away do you really need the most powerful flash? Can having a large flash not hinder your ability to take a properly exposed photo as much as it could help?

Havin a more powerful flash won't hinder you. TTL metering should be giving your flash information to automatically adjust. For Nikon this is done with the TTL-BL setting if outdoors for fill flash. I am not familiar what the setting is on Canon flashes. Although, It's not alwasy "automatic" as there will be plenty of situations where you want to use negative (or positive) flash compensation.

Also, some speedlights have a wide angle diffuser you can flip out, that helps for close distances too (again, you may not always want to use this, but it's a tool at your disposal if your flash has it).