PantLoad speaks the truth. V2 is typically below Vmd, thus is less than optimum speed for best angle. The V2+10 reference puts you closer to best gradient speed, BUT (and it's a big BUT), only if you've ALREADY achieved the higher speed at the time of engine failure.
If engine failure occurs at or close to V2, don't accelerate to V2+10, even though the gradient achieved at V2+10 will be greater after having achieved it, the acceleration will mean 'ducking under' the required gradient to clear obstacles, thus your resultant flight path will be less than that required.
Example -
Failure at V2 = Maintain V2
Failure at V2+7 = Maintain V2+7
Failure at V2+10 = Maintain V2+10
Failure above V2+10 = Reduce to V2+10, then maintain V2+10
Regards,
Old Smokey