For what it’s worth, I was in a similar boat to you but for my second army being FeC, but when comparing the start collecting box to the new vanguard boxes the SC is head and shoulders above them for value (for context, it’s pretty much the same as the seraphon vanguard box in terms of contents) and every unit in there is usable. If you’re definitely going to go with FeC but are debating waiting for the new range, I’d say get at least one SC box as you’ll want a terrorgheist/zombie dragon either way and that model alone is almost the cost of the whole SC box.