@kenny-crane, Those ones you mention are well respected institutions, and I can't say a signle bad word about them. GDAX is obviously more focused on US (as Kraken is on Europe). As of today, Binance clearly leads the way, in terms of volumes, trading pairs and, most importantly, marketing. I say most importantly as it definitely helps them to retain the client base and to acquire new users — what was the last reported number, 6mn accounts? Insane, right?
As for the case I'm working with now, the platform will be regulated, will allow fiat deposits/withdrawals and will focus on security tokens, which is a rare specialization these days. So, full compliance and transparency, an open eye on application materials and green light to all combined and hybrid solutions: equity of digital assets funds, tokens of real world businesses and such.