hoho my next purchase as well, been weighing the pros and cons of the dd7 and hardwire dl8 for too long!
hardwire has more effects, sound quality is much better. 20sec looper.
dd7 seems to sound worse according to many reviews, i heard that the analog mode doesnt sound good at all. and the usual "sterile, cold" boss digital repeats. but, its looper is 40sec. and it has an external tap tempo input.
the hardwire doesnt, no matter what, you gotta wait 2secs to use the tap on the pedal itself.
so im still deciding between the two, the dd7 is much more affordable and practical if you are solely gonna use it for looping. (i dont really know anyone who seriously needs 40sec of looping, 20 is enough). but the hardwire is just.. nice. looks better, sounds better but i know i dont need all of it.
regarding looping sound quality, i havent heard looping from the dd7 yet. but my guess is that there shouldnt be much of a difference.
both pedals cant loop and activate delay after that.
my dd20 can do that, however the looping is only 10 secs, which isnt enough for me at times. im not sure about the akai headrush as well... yep 2 cents!