It’s impossible for us to answer. On the one hand, top privates tend to be generous with As. On the other hand, the general level is excellent so the quantity of reading is going to be much greater and the paper quality you need to produce to get an A will have to be topnotch. So, if your main reason for transferring is academically/intellectually challenging yourself you’ll find that.
A more important criterion would be cost: would the top private universities where you’d transfer be affordable without loans ?