The big draw of ECO hubs (at least for me) is that it's something that can be done in the driveway in about the same time it would take just to service the hubs. And it's just as easy to revert back to stock. Also factor in the price at around $2500 shipped
Where 3:07's will require pulling the axels, dropping the drive shafts, cracking open the pumpkins, etc, etc. Having someone do the work is pricy (especially if they really know these trucks) and the work is mostly all geographically isolated. The cost of the 307's is historically anywhere from $3000-$5000 for just a pair of pumpkins (yeah, the originally cost about $80 ea at auction but "supply and demand"...or blatant wallet rape depending on your perspective). The price may be falling as people shy away from them in favor of the, IMO better solution of ECO hubs. I'd not saying that 3:07's are still not a good deal at $80 each, I'd just rather the flippers who have controlled the pricing up until now keep them. The 3:07's are FAR more complicated to revert back to OEM should someone wish to do so for whatever reason. And shipping a couple pumpkins across the country is not cheap.
Personally, I'd always MUCH rather support someone who is actually making a product.. opposed to just flipping old surplus (especially when it's for big profit justified by "supply and demand").
ECO hubs are a win/win in my book. There's no question as to which is the better/smarter purchase/install, IMO.
ymmv