When I got into this hobby, 2000mah batteries just came out.. but 1600's were the only "leagal" battery. At the local tracks, 1/3 of the field couldn't finish a 4 minute race... even though I prefer engines anyway... that was the deal breaker there!!
Now today.. someone new... run time isn't a factor??
But I do believe noise is the bigger factor. don't think emissions will be the downfall.