If you need to ask this here in public before launching your ICO,,, I would say it is better if you don't even try to do it. You should know first of all what is the value your chosen platform will bring to your project and how it would work out. Otherwise it is simply a token for the sake of a token. No real crypto value, no blockchain tech, another meaningless ICO.
Thanks for your input, I appreciate any and I mean that. First of all, I believe anybody should always try no matter what, so we will do this

Second, I know the difference between Waves and Ethereum very well, as well as the advantages and disadvantages of both of them. But the question was how confusing it would be to hold pre-ICO on one blockchain and ICO on another. It seems I have an answer now

And of course I cannot agree with you on the meaningless ICO. We are building a product that would be better than greedy existing ones. We want to give people all over the world who cannot afford traveling the possibility to practice foreign languages easily and free/cheap. And we also want to give common people the possibility to earn money by providing such practice without greedy platforms and payment gateways robbing a good portion of money they earn. And what is important - we already do this.
Thus, if ICO helps us improve the product and spread the word about it, I won't consider this ICO meaningless. And when the product is successful, investors will be able to earn because the token will be an integral part of the product and there will be demand for it due to its limited supply.