At what point is IV more important than attacks for a Defender Venusaur

Sites ranking Solar higher on def likely aren't looking at certain effects like type advantages/weaknesses , coverage vs. likely attackers, or potential dodging by attackers

Sludge Bomb is ranked so high here b/c they actaully consider type coverage and common sense. It gets STAB and does full dmg to like, basically everything. Since odds are they're attacking you with a weakness like Fire/Flying/Psychic, etc. then you have to consider which performs better vs. those.

Long story short I love Venusaur but powered up a defender and wouldn't recommend it. Guaranteed first to b elkicked from gym

Go for number 2, 91% RL/PB

Petal blizzard is the best defensive move against neutral opponent. But it is very very likely that your venusaur will be attacked by a Pokemon who resists grass (pidgeot, flareon, arcanine, dragonite x2, charizard x2, exeggutor ). So it make sludge bomb better.

But venusaur will be a bad defender anyway and low Cp one in addition. So if you really want one I would choose a already high level razorleaf high IV one. Number 2 is good.

One consideration is what is the entry point for local gyms. What cp level will get you at least 2 or three paces above the bottom defender in most gyms?

If you can get Venausur to that level then for me he becomes a perfectly viable defender.

Each charge move has pros and cons - I don't think any of them are bad. Solar beam hits very hard with STAB, and will still do a fair amount of damage even if successfully dodged.

The only thing I try to do judge a "Defender" on is its ability to break up strings of defenders.

The issue becomes that because the common defenders like Vaperon, Gyrados, Rhydon have so much more base CP than Venusaur. You need to be higher level than your average area to make Venusaur worth powering up.

Venusaur for me anyway, has never proven an amazing defender and I think in the end game his CP is kinda low compared to others. If you do have your heart set on a Venusaur defender, because I believe if you think a mon is cool then go for it because its a game at the end of the day, then I would say RL/Sludge Bomb is the best. Just speaking from experience, when I attack a Venusaur with my Arcanine or Charizard, Sludge Bomb really can catch me by surprise and makes me use potions if I don't dodge.