For me building comes first, animals second, guests are.... unnessessary (for me at least). I don't look at them closely (why should I?), so I don't care if they can "express themselves" or not. They are just a pain, because they are clogging everything up and getting stuck. And I would rather have them look lifeless and stiff (and being about 10 to 20 times less many per default) than causing me to fall out of my beautiful realistic zoo into a silly cartoon. But as you can keep your guests off in sandbox, this is not so much annoying as the staff.