TL;DR: You're better than your friend.
Let's say for whatever reason, Silver 1 in EUW was the same as being Plat 3 in EUNE (which it isn't, but just for example). You'd still be better because your friend has a 49% winrate you have a 55% winrate.
So yeah, it's pretty much not even a debate at this point. He might be like Gol 4-3 in EUNE, but this is a MAYBE. but he'd be a division lower than you still.
the elo difference between EUNE and EUW only starts to become apparent in like D2+ and starts having a significant difference in Masters/Challenger (and that's only because the really good EUNE players switch over to EUW), but like, that's such a small portion of people that it's not even worth mentioning for comparing the average player base. So Plat 3 EUNE is basically still Plat 3 EUW.
Nothing a few 1v1's can't fix though. I'm a high Plat/low Diamond support main, but I can still kick the absolute sh-t out of my gold friends, even on their mains. I see Yasuo's/Zed's/Ahri's in Diamond all day, what's a gold player going to do that I haven't seen already? Silver 1 vs Plat 3 should mean you wiping the floor with him. This should get the point across pretty quickly. I haven't heard the "you're a support so you were carried" line in a long time.
