The "best" equipment to scan slides? A drum scanner, of course. I've seen used ones that were decent go for as little as $12,000 lately. Now, assuming you don't want "best," just "OK for the price," I have some thoughts. I scan 35mm, 120, and 4x5. For 120 and 4x5 I use an Epson v700 with the betterScanning.com wet mount holders. This makes decent scans, up to a 20x25 with 4x5 sheets. For 35mm I use a Nikon Coolscan V. It's slow but very, very good. Only available used and they go about $800 or so. I've been considering selling mine and buying a used Nikon 8000ED for about $1,200. It does 35mm and 120. I've been shooting mostly 120 lately.
For you, assuming you don't want to spend the $23,000 for a new Hasselblad Flextight scanner or even a used Coolscan V, I'd suggest trying to get B&H to exchange what you have for a Plustek 7400. It's a decent scanner. Not the "best," but I think it will do what you want.
http://www.bhphotovideo.com/c/...lm_7400_Scanner.html
I would not use a flatbed scanner for 35mm unless you are doing them for 72 dpi web use or something. Remember that I'm only getting decent enlargements of 5x from my v700. That would translate to a 4x6 print from a 35mm neg, approximately. Now to push this into an entirely different direction than the advice you'd normally get on a railfan board. If this is to be a one time deal where you're scanning just your best slides and aren't shooting anything new on film, tell you what I'd do. I'd buy a pretty good scanner such as the Nikon Coolscan V, or something like this would be perfect for the job:
http://www.bhphotovideo.com/c/..._Slides_Scanner.html
Find a USED one on ebay, buy it, scan all your stuff, and quickly resell. I bet you'd be out very little money and would have great scans in a short time with something like this. I buy and resell stuff like that often on ebay. I don't own a Nikon 500mm f4 lens any more, but if I have a special need for one I just buy a used one, then quickly resell. Sometimes I make a little money if I time the purchase right. The trick is to buy used, then resell in the same condition you got it in.
Kent in SD