I didn't find dissection particularly helpful. As people have said, you just get given a body, the tools to dissect it, and if you've brought one along, a book. It's enlightening to see how the body fits together and see the actual organs, but I think that prosections and actually just reading the anatomy books can help you with that. Most of my anatomical knowledge in the end is based on visualising how things looked in books or on models. I've never once had a flashback to dissection or thought 'oh yeah, that's what it looked like!', and am not convinced it helped me remember anything. It was just a very unusual life experience.
IMO models, prosections, that plastination type stuff and importantly 3D computer software would be ideal.
About the only thing where I think dissecting a cadaver > prosections is that you discover the secret life of fascia and some of the conceptual body cavities which can only be seen when you look at the body as a whole, I think. Generally fascia etc. is peeled off or generally hard to conceptualise on a prosection, because you can't see where it linked up to.
Perhaps it depends on you as a learner but, with the greatest of respect to the people who donated their bodies, I don't think it was a useful exercise for me. As mentioned by others, I don't think it's an essential opportunity to have or to make choices based on. If you do it, fine, if you don't then I don't think it will hinder your ability to learn anatomy, pursue a surgical career or whatever you want to do.