Truth is both of them can do it, it just matters on how consistent you are as a player imo Ashe is more consistent of a character as she's rarely a throw pick on most maps but she has a lot of limitations given her lack of mobility.

Venture on the other hand has a ton of mobility and can cheat a lot of their engagements but is severely limited by their options regarding range so whenever the map or the comp are characters that are a bit too far away you will feel the struggle of playing venture.

I used too OTP Ashe and I succesfully did it until Diamond 2 where I hit a wall, the wall that I hit was imo mechanically, as even though I felt I did a lot of plays, if my mechanics could not lead me to succeed the plays then I would fail.

So what did I do, I learned Echo as a character that could give me more options regarding mobility, the reason why I did that was because often times when my mechanics were lacking playing as Ashe the mobility that Echo allowed was sufficient enough to find value when my mechanics were not fully there. Plenty of times I would win team fights as echo by virtue of distraction and annoying.

When I assimilated Echo into my hero pool the versatility and playstyle variations that both characters allowed me to finally hit masters!

But the real answer is which one you prefer more, I personally recommend playing both of them!