I was thinking about this earlier today--Trump will likely do stadiums. It's hard to see Clinton doing that on her own. Will she be able to match crowd sizes if she brings in other people? Will it matter? I don't think it would necessarily have a big impact, but I just remember back to 2008 when Obama had one massive rally after another. Obama made you feel like you were a part of something, which is one thing I think voters want on a basic level, regardless of political leanings.
Will Obama be able to pack in the crowds for her? What about a dream event with Sanders and Warren? Hillary just doesn't seem like the type who would do well in a huge venue.
The size of venue doesn't matter; if you have a junky candidate, you'll have junky turnouts at your functions. Hillary will never generate the kind of enthusiasm that a Trump or a Sanders can. But it won't matter: the people who support her will continue to support her, and the people who don't aren't interested in starting to. Her focus should be on ways of not losing people to Trump, because I'm beginning to wonder if even folks who don't necessarily appreciate Trump's temperament will have to think long and hard about pushing the button for Hillary Clinton.