Yes, they will provide more subtle benefits than just flavor. As Dan has pointed out, and I agree, adding oak in primary helps stabilize color and does affect other flavors - not necessarily oak. Oak provides tannins for aging and structure. The forward "Oak" taste we typically refer to in wine largely comes from the toasting of the oak that provides smokiness and wood flavors. The level of toast brings out different amounts of vanilla and other "oaky" flavors.
It's actually a bit complicated as different oaks and different toast levels all affect the flavor and tannin structure.
Unless you are aging in oak barrels it is more difficult to integrate oak. Using powders, chips, cubes and staves is good but does not provide the exact same affect as aging in a barrel where you also get concentration by evaporation and microoxygenation.
I find oak from additives integrates better with wine when added in the primary. If it isn't "oaky" enough using staves or spirals after fermentation can add more and is easy to control.