What is better? I pretty much would trade for silver eagles and then I don't have to pay sales taxes. I know I could get more for them on ebay but after fees and sales tax on the Eagles I think it would be cheaper
Coin dealers are just a middle man.. you down grade your stuff and up grade theirs for selling. A reasonable number would be $4.00 per 40%er & $10.00 per 90%er. You might be able to get some more than that for 90%ers depending on location.
When it comes time to sell, I'm 99.99% positive you'll make more money by avoiding coin shops. Most can't pay anywhere near spot as they have to make a profit. You'll do better at coin shows, the big metal exchanges, and/or right here on this forum.
As far as trading, at least in my experience, coin shops want to profit off you at both ends. What I mean is that they will want full retail price for their items while only giving you a fraction of what your items are worth.