They do. It's in the comparison of the medals on the purchase page.

they increase stats

The direct increase isn't very large, but there is some. They also grow at a faster pace due to various perks. And... well, if they can ptw to get medal, they could also just buy power.

Jonin medal gives very little direct power (only about 100). The the guy is gone for 2 months and suddenly got a ton of power over you; he most likely bought power from other sources.

the stat increase is minor if u dont use it right. Its rightly just a convenience device, and secondly a coin boost if u do ninetails with the medal the boost over time will greatly help in advancing your eightgates, gear, donations*. Donations are very important as if u can spin that wheel and get coupons you are boosting yourself with a premium currency. Efficiently doing this is important to keeping spending (irl) low and maxing growth potential: Having a ninetails team is important. Just take it in consideration that participation is still king.

She says tht she doesn't spend money on anything to gain power. Just use money to buy/re-activate her Jonin Medal and tht's it

So like if her and I leveled up at the exact same time, her stats would increase a bit more due to the medal? Same with anything tht gives them more power?

Stats from jonin medal is static. 60 hp, 30 attack, 30 nin; which is only about 100 pow; no more. You do not get any additional pow based on level.

You can gain a lot of power quickly from going through ultimate training and such; but a big power increase is definitely not because of jonin medal.
This post was last edited by IamAscrub at 2017-4-25 11:17

Well, my friend's not any farther than I am in Ultimate Training. I'm also maxed out in Group Skills and they are not. My Bond Points is also way higher as well, and tht's a little extra power. So I just don't get how their power could've increased so much, so fast, after having been gone for 2 months then. :\

Either from using stocked up mats for things like battle armor/refines; or just plainly buying power. Just because someone say they didn't buy it doesn't mean they are not doing it. You can gain a fair chunk of power very quickly by spending coupons/ingots on charm packs; if you didn't finish ultimate training, for example.

Inspect them and look at their battle armor level/rank, magatama, refines, rune stones, purifies, summon runes, etc. I think you are able to view almost everything besides cultivation, 8 gates, tactics level, ninja tools, mood, group skills, group summon, and exact character advancement. Group summon won't matter if you're in the same group and you already said your group skills are higher (although that's taking their word for it).

You should be able to compare your stats to theirs on each of these to get a general idea of where their power is coming from. If you don't see a difference in anything visible, it's likely one of the few things you can't see (like maybe they bought a bunch of tactics pages and leveled it up a lot).

If you are further in ultimate training than her, it's easier for her to get power out of ultimate training. Same story with group skills; if you're maxed with group skills but she isn't, she's still getting power out of it and you don't (20-30 power a day if you can buy it everyday). Same story with bond points; if she's lower than you, it's easier for her to get power out of it.