William, I'm very fond of any little bulbs with blue blooms and have various scilla, chionodoxa, and ipheon varieties in the garden. The scillas and chionodoxas definitely perform more vigorously and increase nicely both from offsets and seedlings. The ipheons have been slower to increase, but have returned well and are forming thicker clumps. They bloom later than the others and I do enjoy combining them with other plants that bloom at the same time, but if I had to choose I would pick scilla because they provide such vivid blue when there are few if any other plants that color blooming. Ipheon bloom when lots of other bulbs and perennials are providing color, so I wouldn't miss those as much. I have found the species I. uniflorum increases faster than Wisley Blue and Rolf Feidler.
