Scrypt based coins are useful for low end gpu miners or the "average joe" type miner if you will. Most people dont have much of a chance to mine the sha based coins with all the new asic technology coming out faster than ever before.

There are fpgas in the works for scrypt based mining but as far as I know there are no asics just yet. This leaves a fairer game for newcomers to crypto currency.

Whether they are premined or not it is what is done aftwards that really proves a coins worth if it stays around and grows an economy and services to compliment it. It is still early days to give a full answer to which coins are going to be long term and which ones arent.

Remember in your show to be speculative towards which coins may or may not be "scam coins" and be objective in your evidence towards it otherwise you will upset a lot of supporters for each coin. Whether it be support through greed or interest in the coins future you dont want to alienate any listeners like that.

This ones going to take a lot of research