I used to have an Inverted V antenna in my loft for 11m and it was pretty awful for local CB contacts but absolutely awesome for DX especially with good propagation conditions and SSB use.
That said I did get some Continental action on it a few summers ago using FM on the Euro/CEPT/Mid block frequencies but again on some sporadic 'e' DX.
A contact that used to hit me S9+ on a vertical dipole dropped to around S7 with the Inverted V and another that was a good radio five but S5 on the vertical all but disappeared into the noise with the inverted.
That's just my experience and others are bound to have different opinions probably relating to antenna theory, maths, numbers etc.
Hope that helps if only even a little.
All the best,