I installed a ghost ring on my Mossberg 500 years ago. The cost of just the part was more than the extra $50 installed you mention.
In comparing the two, both ghost ring and bead front sight only, I think the ghost ring arrangement is faster for acquiring the target and aligning the sights. For one, your head is more upright rather than scrunched down to sight down the top of the shotgun with the bead only models.
The ghost ring arrangement does a great job at getting accurate hits with slugs 50-100 yards out.