Ok since i played fair amount of games on both server at that elo (silver-gold) i can estimate a judgment here that:
toxicity :on EUNE u will get like 60% "toxic" games compared to 40-50 % on euw ,it can varies because it depends at the times u play the game at ,day/night and weekend or not (weekends are generally more toxic from my experience on both platforms and FOR ALL GAME TYPES for obvious reasons !) .
Understanding the game and the current meta : I have to go with EUW on this for many reasons (not big lead since we are still talking about silver goldish) ,more people on EUW that can actually talk/understand english which imo lead to that people on EUW knows how to jungle ! yes i noticed big difference for junglers (at least who mains it ) on EUW even at plat league ,Now for EUNE there is a noticeable gap in mechanics/plays between players in the same div/MMR due to not taking the game serious and not having a team to play with .
Queue times also can be less for EUW since there way more people on EUW
There is more differences ,but all changes for person to another's perspective :)