More vigorous growth will be seen in more sun.

Try them in both places.

Hellebores are tolerant of shade but unless you are in really more southern zones they appreciate a fair amount of sun. I'm situated on a south facing slope and many of mine get nearly full sun until about 3 pm. as the sun drops below the tree line on the west. They thrive in these conditions, actually better than those which get only early morning or shaded light.

Agree with the above. While the hellebore hybrids we grow now are a long way from the species plants they were derived from, they appreciate similar growing conditions. And if you research the nativity of these species, you will find that they are seldom found in heavily shaded condiitons. Most are native to woodland verges - that transition zone between an actual forest or wooded area and an open meadow. And more than a few are found in open, rocky moutainous areas as well as grassy steppes. So as noted previously, while shade tolerant, they do not require shade. There is a difference!!

One of the most recommended sitings for hellebores is beneath the exterior (edge) canopy of a large shade tree. Here, they benefit from uninterrupted sun during their emergence from late summer dormancy in winter, flower profusely before the trees leaf out and then appreciate the dappled shade after the bloom cycle and as summer temperatures and sun intensity climbs.

I have grown hellebores in full sun and in partial, dappled shade and both seem to bloom equally as well. Those in more heavily shaded locations are much stingier with their flowering.

I would also try both locations and see which works best for you. FWIW, a north bed planting location is not necessarily considered heavy shade even though it may receive little or no direct sunlight. Often, this is a very bright but indirect light situation, which should be fine for hellebores