Is there a huge difference between a pokemon with 70 IV and 100 IV?
It really depends on who you ask. Some think it does, some think it doesn't. The best thing you can do is read all the info available about IVs and make the decision yourself.
It is agreed on however that it makes very little impact on the actual battle. If you're asking about the CP difference you can find the exact amount using the cp calculator.
It really doesn't depend on who you ask because it has nothing to do with personal opinions.
A lvl 30 Dragonite (Dragon Breath/Dragon Claw) 100% IV is 21,6% better than same level, same moveset Dragonite with 0% IV. By better I mean that it will do that much more damage before fainting.
So you will definitely be able to tell the difference. The difference will be even bigger for Pokémon with lower base stats because additional 45 points of base stats will be proportionally higher.
I don't know about you guys but over 20% difference sounds huge to me.
I used the sheet with old stats and had problem accessing Pokemon_Data, but was able to make the change in Move_Sets. (Did some rounding, adjusted all base stats with -11, which is close enough to get the general idea.) DB/DC Dragonite's TDO went from 388 to 317. So yea, 20% seems about right as surprising it is.
Thi biggest difference is that IV is something which can't be changed. You stuck with whatever you got. Which, if you put it into perspective, there is a good chance you will eventually find better IV one eventually. And when it happen, you might feel disappointed with investments to your old 70 IV one. Unless it's something like Snorlax\Lapras, or attacking pokemon not placed in gyms. It's not much difference in strength, but it is difference in CP, it might be as little as 100 CP, but that important in gym placement. And will become even more important with time unless system will change at some point.
The calculator at https://pokeassistant.com/main/ivcalculator will show you the actual attack, defense, and stamina stats of your pokemon and how they compare with the best and worst at that level.
The actual distribution of IVs is probably more important than just the total percentage. And that could differ by pokemon.
For example, I have a low level 64% IV Snorlax, but after rechecking this afternoon I saw that it was 15atk/14def/0stm. Snorlax's base stamina is already through the roof. If any of his IVs are going to be 0, stamina is his least important.
Other pokemon like Alakazam with a relatively low base stamina will benefit a lot more from a high stamina IV.
For gym placement IVs are more important for Pokes that have a low max cp.
If you are planning on eventually powering it up to level 39.5 then the max cp will be impacted by the IVs. If you're not planning on fully powering it up you can compensate for the slightly lower IVs by powering it up slightly further to get equivalent CPs e.g. to roughly match the cp of a lvl30 Gyarados with 15/15/15 you could power up a 10/10/10 Gyarados to lv33.
to roughly match the cp of a lvl30 Gyarados with 15/15/15 you could power up a 10/10/10 Gyarados to lv33.
OMG. I could not believe it and so i used the calculator just to be sure - it is perfectly true!
So the difference is huge, in this case, it is
34k dust / 32 candy to get the same cp, or, at the same level 30, the difference are 2812 to 2690 cp.
Does 100ish cp make much of a difference between gym slots? In my area generally not, but for some people it might. Don't forget this is the difference between a 66.6%IV and 100%IV Gyarados - generally you're only likely to be evolving 80-85%. An 84.4% IV would only need an extra 1.5 lvls powering up to exceed a 100% IV Gyarados's CP...
Please read my more detailed comment just below.
Gyarados is somehow special, as it needs so many magykarp, it seems reasonable to assume everybody to develope a Gyarados has a good high-iv-magykarp.
This is not true for other pkm with lower candy-cost to evolve or with pkm you can't evolve (tangela, lapras, snorlax etc.) There, the differences ov IV will be bigger.
Assumptions:
Pokemon is a hypothetical, but strong one with 190/190/190 Base-Stats.
We compare now IV 10/10/10 (66% IV) to 15/15/15 (100% IV)
Conclusions:
The new Pokemon would be
205 / 205 / 205 (100%) or 200 / 200 / 200 (66%)
We can calculate two values:
CP at level 40:
[Edit: CP without level reduction factor instead of level 40 is true, but does not matter here, as the factor is the same for all cases, as long as level is the same]
CP = 4202 (100% IV) / 4000 (66% IV) The difference are 200 Points = 5%
Damage done, bevore Pokemon faints (not really defined here, but can be deduced from simplyfied damage formula as) being proportional to
ATT x DEF x STA.
There the difference is 7,5%
So we can conclude, that the difference of IV 66% to IV 100% is
5% CP-wise
7,5% damage done as defender
This was the symmetrical case of a hypothetical elite-stat-pkm.
If distribution of a pkms Base-stats is highly assymetrical or the Base stats are lower, or IV-distribution is not even, the difference tends to raise.
So regard my 5% / 7,5% as rule of the thump, real values can be easily calculated based on a specific pokemon and tend to be slightly higher.
[Edit: 190/190/190 is not the upper limit for pkm. For real big ones as snorlax, rhydon and dragonite, the effect is smaller than 5 / 7,5% ]
[Edit2
In relation to basis stats, IVs are small. Thus, i linearization is adequate for a rough estimization. With this restriction you can estimate a 0%IV-pokemon in comparison to a 100%IV-pokemon to be
15% weeker CP-wise and
22,5% weeker as gym-defender]
