>>20018191In most cases you can. There are a fair few places where they force you to wander into both trainers, though. Not to mention times where you accidentally walk into one of these situations.
Basically, my complaint is centered around the fact that I'm not as fond of double battles, and Emerald has a larger focus on them than R/S does. I didn't say that reason alone put Emerald on my list of "worst games ever," just that the system was annoying and that I prefer the games without it, such as Ruby and Sapphire.
Believe me, I still love Emerald. I just prefer Ruby and Sapphire, and three small reasons are all that it really takes. As much fun as the expanded Safari Zone and Battle Frontier were, they weren't enough for me to have preference for Emerald.