the CPU instead of the GPU
well a programmable GPU is always faster as a CPU because these mathematical problems need only a very small part of the cpu
and your gpu has ... around 200 "virtual" cores instead of 8 or 16. they are always faster.
the problem is, if you use a "CPU version" you don't know anyone else has a gpu version of the same "coin" or if a gpu version will released later
and if this happens the value of your "coins" decrease. All because these mathematical problems which are the basic idea are solveable a lot faster on gpu.
Take bitcoin as a example. Nowadays its an energy waste using a cpu but even with gpus you can wast energy because there are already specialised fgpa boards for bitcoin mining.
Well to be honest I think the times of "mining" these value is over, the difficulty has increased to much and some calculations show
you can only earn money if you calc 2 years in the feature.
For me "buying" something to mine bitcoin (even its energy) is the same as speculation on the stock.
If you want to speculate you can try to mine bitcoins / litecoins / any coin but you can't calculate it as real income. You may have luck or you may not have luck. Its the same as the stock. You can earn money , you can loose money. If you want to try your luck its your own decision.
Back to topic: just want to say there can't exist a cpu version of any coin