Physical games can have more extras on the disc, extra language options. The digital version is usually the leanest version to keep the size reasonable. Physical games can also play cut scenes from disc while loading the next level from the hdd install. Or stream from both disc and hdd install to speed things up. 2 locations to get data from is always better then 1.
However I have no clue how DW8 was made. It could work the other way around too, all loading from disc without an install which makes the physical version slower. Since it's on 360 too, which doesn't have a mandatory hdd, and pc, where it always runs from hdd, I doubt it's optimized for using both disc and hdd simultaneously.
You'll have to wait until DF to find out, I doubt there will be much of a difference though. The physical copy will probably have a large HDD install and will perform the same. Simplest solution for multiplat titles.







