Bitcoin Take Over Threats- 51% attack because mining is ASICs concentrated and ASICs foundries could be purchased with unlimited fiat. Note also ASICs can't be re-purposed as PCs can, i.e. each ASIC only works for a specific coin design.
Meaning the CPU-only coins are a more flexible investment. Your hardware is resalable to the general PC market too.
Note Scrypt is not cpu-only.
Cuckoo is also not cpu-only, it is memory-only.