This is weird, which Pokemon has these, none?
1. Vine Whip + Power Whip
Vine Whip is much better than Razor Leaf (slightly better DPS, but its quicker so you can evade)
2. Razor Leaf + Solar Beam
This is like number 1, both moves are slightly weaker and slower.
3. Petal Blizzard, slightly better than leaf blade.
You have actually already ranked them in your question, hehe
Edit: I just saw you said solar beam is better than power whip, I disagree. Power Whip has slightly better DPS and it's quicker so you can evade/less of its damage is wasted.
Rank these Grass Attack Combos
As title says for "Attack" once you setting aside the Obvious. Vine Whip / Solar is the best combo how would you rank the remaining Grass Options.
Vine Whip + Power Whip
Razor Leaf + Solar Beam
Razor Leaf + Petal Blizzard
Razor Leaf + Leaf Blade
Answers
I thought so. Vine/Power is very close to Razor/Solar (almost identical, but much slower) The rest would depend on the pokemon stats. Tangela in general has the lowest ATK of the grass pokemon, Victreebel the highest. I assume Tangela with Vine/Power is much weaker than Victree with Razor/Solar, but still fun to use ;)
I'd put Razor Leaf + Solar Beam above Vine Whip + Power Whip tbh. I found Power Whip to be a pretty underwhelming one-bar charge move, especially when compared to the destructive power of Solar Beam - this difference is pretty evident when I'm using Tangelas. Razor Leaf is a slow move, which might annoy some, but it still deals nearly as much damage as the more practical Vine Whip.
Vine Whip is the best quick grass move, and I'll go against the grain here and say that two-bar charge moves are much better than Solar Beam. For one, you can dodge enemy quick and charge attacks, and two you don't have to worry about wasted energy gain as much -- since you likely won't be able to fire off your solar beam as soon as you're ready to use it (unless you want to eat a charge attack from the enemy mon).