Gigarec is MUCH nicer than HD-BURN. Since you can select the "level" for Gigarec (20,30,40% more space, I think). The lower levels can be read by far more drives than the higher levels. And HD-BURN? Not bloodly likely.
Gigarec just reduces the pit size on a CD; HD-BURN also uses a different form of error correction; a much worse form. Out of about 100 or so HD-BURN discs I've made, about 1/3 where at least partially unreadable.
Check out the old Plextor Premium review here; it has more info on GigaRec.
Soon to be proud user of Mandrake 10 (again!). SuSE 9 sucks!