I am pro EMS and think that there should be more!! I didn't enjoy vet school clinics for a number of reasons which I won't go in to. I think my time would have been better spent doing more EMS in place of certain (not all!) rotations.
EMS is the most accurate representation of what 90%+ of new grads will be spending their first few years in one way or another. Learning to deal (or how not to!) with clients is the most important skill to master. Rotations don't expose students to enough of this sort of thing. Doesn't matter how good you are at the job, if you can't talk to the clients and keep em happy, you sure know about it. You also learn lots of other skills on EMS, surgical skills, day to day practical tasks, practice management, record keeping, learning which diseases are common! The list is endless.
The biggest limiting factor is in finding a good placement where the vets allow you to do things and it's of course important to make the effort and sieze every opportunity to learn.
Just as an addition, I hate chickens and pigs & not treated a dog or cat since vet school!