In my opinion. If you are going to buy either neo or gas with fiat/other crypto now for use at ICO time I suggest to use Gas. This is because ratio of gas to neo is 3 to 1 right now when it used to be 2 to 1 some months ago. Plus, as people want to get the most out of their 1000allocation they would probably use gas as it is divisible, hence the pre ico pump for gas compared to neo will be slightly higher.