Upload & Sell: On
The only two FW800 CF readers I've encountered in the wild are the Sandisk Extreme Firewire 800/400 (which I own and have enjoyed using for the past several years, despite encountering a bent pin...one of the hazards of CF technology), and the Lexar Professional UDMA FireWire 800 both of which, I believe, are out of production. I have seen both of these pop up sporadically on the B&S board and they can be hunted down with some small effort online. The Sandisk, if I'm recalling correctly, went for about $59 new, though I may have gotten it on sale at some point. I've seen used prices range from $40 (a recent B&S sale) to nearly $100 for that reader.
As for USB 3 on that MBP, if yours is a 2012-or-later model (e.g. MBP 9,1 or 9,2 or later), you should be good to go. (You can check the model version in your System Profiler application, Apple Menu>About This Mac>More Info...) I haven't gone USB 3 as of yet, so that Lexar Reader that EB-1 recommended might be the way to go for you.
However, if you're bent on going with FW over USB 3 I wouldn't sweat the speed differences between the two, judging from the test numbers I've seen the few seconds difference in real-life usage would be meaningless to me. This is all covered ad nauseum with a slew of cards and 25 different readers over at Rob Galbraith's site...
Rob Galbraith DPI: Card-to-Computer: CF Readers:
...the page hasn't been updated since 2011 (so, no 1000x cards tested) but you'll get the gist of what I'm saying from his test results. FWIW, he mentions a few other FW800 readers there, as well.
Anyhoo, I hope this was helpful! Let us know what you decide...