It's important to note a critical distinction between the two:
Top Rated Seller is an account level status. That is, you're either a Top Rated Seller, or not, regardless of any settings on your listings. It does have some benefits, but not the fee discount, which is certainly a major advantage for anyone selling at a decent volume.
Top Rated Plus is an item level status. That means a Top Rated Seller can have some items listed as Top Rated Plus, and some not. Those items that are Top Rated Plus will get the 10% fee discount (note that it's 10% off whatever fee you would have paid, not a 10% drop in the fee rate, as in you don't pay 3.25% fees instead of 13.25%, you pay about 11.93% in fees in the categories that would normally be 13.25%). Also, some categories don't get the badge even if you would otherwise qualify (and those categories may have different requirements for the returns to qualify, such as some categories you can have buyer-paid returns or shorter return periods and still qualify).
@premiermedia, definitely read over the links that @wastingtime101 shared very thoroughly. There's a lot of detail that's worth knowing about.
For us, offering the Free Returns for 30 days and a 1 day handling time was no problem, especially since we save far more in fee reductions than we lose in the returns process (particularly since we can resell many of those items quickly, so we're usually only out the shipping, though sometimes that's both ways depending on the reason for return). For a smaller seller or one with items that cost more to ship, however, it might not be worth it to do free returns, and you might be better off just being a Top Rated Seller but not adapting your listings to be Top Rated Plus.
