VHO is just about obsolete by today's standards. The main reason is because you can get more light out of T5's by putting individual reflectors behind each bulb, and you can get a lot more bulbs over the same area.
Since you already have the ballasts, you could put them to work for your system, but those original Ice Cap ballasts are no longer being made. This could make replacing tem with an equivalent a little tricky, although there are plenty of other ballasts out there.
You also have an additional factor. LED lighting is going to cost more initially, but long term cost a lot less because of the much lower energy consumption and not needing to replace bulbs. If your going to buy new, LED lighting can be a much better choice than VHO or T5.